Best Practice Question - How do you prefer to pass a bunch of options to a function?
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcI'm not sure that I've ever needed to do that other than in cases similar to database connection strings -- like a factory of some sort -- and then XML works. :-D
@""Obviously, the problem with "but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists)" is taken to a whole new level. :omg:You'll never get very far if all you do is follow instructions.
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcI think I have some internal, arbitrary rule that says; If the parameters are basically unrelated except for being passed to that function, then leave them as individual arguments, well defined by their names. If the parameters are related, then wrap them in some structure or other. In other words, I wouldn't wrap parameters in a class or struct just to make the function signature smaller or more legible, but I would do so if it made sense for the parameters to be combined; The danger of wrapping them is that you replace a long function call with a complex struct creation, to no real advantage - reading a method signature with meaningful argument names is self-documentation; the same method with a single argument called "necessaryInfoToDoTheJob is less descriptive!
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When Dealing with Microsoft related programming products creating your procedures with the parameters (Sender as object, e as eventArgs) as an extremely recommended practice, and have your parameter class inherit from system.eventArgs. This way your code naturally interacts with windows runtime components.
Except that you have created event arguments for use with none events. The sender is probably going to be completely useless.
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I think I have some internal, arbitrary rule that says; If the parameters are basically unrelated except for being passed to that function, then leave them as individual arguments, well defined by their names. If the parameters are related, then wrap them in some structure or other. In other words, I wouldn't wrap parameters in a class or struct just to make the function signature smaller or more legible, but I would do so if it made sense for the parameters to be combined; The danger of wrapping them is that you replace a long function call with a complex struct creation, to no real advantage - reading a method signature with meaningful argument names is self-documentation; the same method with a single argument called "necessaryInfoToDoTheJob is less descriptive!
:thumbsup:
Wrong is evil and must be defeated. - Jeff Ello[^]
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. Marc -
I'm personally not a big fan of it, but in .NET you have optional parameters. They look like the example you showed in Ruby (but I don't know if they're the same thing since I don't know Ruby). For example:
private void SomeMethod(bool useThisOption = true, string optionName = "") { // ... } private void UseOptionalParams() { this.SomeMethod(optionName: "MyOption"); // useThisOption is true by default. }For more information: Named and Optional Arguments[^]
It's an OO world.
public class SanderRossel : Lazy<Person>
{
public void DoWork()
{
throw new NotSupportedException();
}
}I believe that strictly speaking, you do NOT have optional parameter in .NET. You have it in C#. But it is handled solely by the compiler, at compile time. Sort of synthetic sugar. (Or sugar-free, since we are talking about parameters who are not there in the source code.) In the .NET assembly, noone can tell whether the value specified as default in the function declaration was really defaulted or specified explicitly by the caller.
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In most cases I consider a large number of parameters (let say over 8) as design flaw, however it is possible that you end with such a list, in which case I would use struct/class...
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)
In the old days, I was working with a Fortran compilers where we had to push the release due to one (important) customer who had run into a limitation of the previous one: It could take only 99 (ninety-nine) parameters. The new version could handle 128 parameters, which was sufficient for the immediate needs of the customer, but the design allowed expansion to 256 parameters. If there ever was a case for Fortran COMMON blocks, I would call this a candidate. (Don't take me wrong - I am not suggesting using COMMON blocks as good programming practice. Nor is 100+ function parameters.)
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I would have to go with wrapping the parameters in a struct/class. That way, I can put all sorts of validation in there that gives the object some context.
Some more advantages; it's more readable when there are lots of arguments, one can easily modify the parameter-set without having to touch each method, and one can even inherit a new set of parameters. EventArgs - wonderfull example.
Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^]
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcWe have been using the struct practice for years, and I am personally strongly in favor of it. I would like to add a few comments/modifications, though: First, a set of options is not a function declaration issue, but a system data design issue. Two or more functions referring to, say, page layout properties should not declare "their own" parameter structs (possibly overlooking some essential parameter). The set of options affecting page layout, say, is one well defined set for the entirre application (or even more). Second, you should never slump together completely unrelated options in one struct, even if one function (or even several) inspects them all. One option struct defines page layout parameters, another one typographical characteristics, a third one the current user. So you might end up with "several" (i.e. a few) option parameters, but not a hundred of them. (For all practical purposes, this second point is also a requirement for my first point.) Third, as software develops, new options will be added. For an exported library function, it must be prepared to handle calls from applications both newer (supplying a larger struct with added and unknown fields) and older (supplying structs with missing fields) applications, and be able to handle them both. So the struct must identify the version. So one of the fields in the option struct is "This is format 3". An alternative is "This struct contains 44 valid bytes of parameters. The very best is to include both: This struct contains 44 bytes of parameters of format 3" - then you can add parameters in format 3 as long as the extensions are fully compatible, and bump the format code only when an incompatible extension is introduced. So the caller must fill in two extra fields, but then again, the same declaration can be used twenty years later. (Don't expect anyone below thirty to see the value of that...) Another alternativ is of course the Win32 API way: Start with MyFunction. Then, when one option is added, call it MyFunctionEx. After the second extension, make it MyFunctionEx. After extension eight, it is MyFunctionExExExExExExExEx, and so it continues :)
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcI think it's important that there's an easy way to find which options are defined. I've had issues with Javascript libraries that take an object as a parameter, and expect you to put the right properties in there (the XMLHttpRequest AJAX handler does this iirc). In a statically typed language like C# or Java (or even C, Delphi, C++ etc), it makes sense to use a struct or class (using those words in their C# meaning) for groups of parameters with values, and a flagwise enum for those without. If you don't have enums then the old school approach of constants set to the appropriate bit values and using | to combine them is fine too. The grouping is important, it shouldn't just be public struct StuffUsedByThisFunction, it should have some semantic meaning even outwith the context of the function call. In dynamic languages the convention seems to be dictionaries with lax validation. I agree that this is often unhelpful, but it's encouraged by the object model in those languages which doesn't really do static declaration of valid members. I've not really worked in those languages enough to have developed a good solution, though.
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I think it's important that there's an easy way to find which options are defined. I've had issues with Javascript libraries that take an object as a parameter, and expect you to put the right properties in there (the XMLHttpRequest AJAX handler does this iirc). In a statically typed language like C# or Java (or even C, Delphi, C++ etc), it makes sense to use a struct or class (using those words in their C# meaning) for groups of parameters with values, and a flagwise enum for those without. If you don't have enums then the old school approach of constants set to the appropriate bit values and using | to combine them is fine too. The grouping is important, it shouldn't just be public struct StuffUsedByThisFunction, it should have some semantic meaning even outwith the context of the function call. In dynamic languages the convention seems to be dictionaries with lax validation. I agree that this is often unhelpful, but it's encouraged by the object model in those languages which doesn't really do static declaration of valid members. I've not really worked in those languages enough to have developed a good solution, though.
Dependancy Injection!!
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In the old days, I was working with a Fortran compilers where we had to push the release due to one (important) customer who had run into a limitation of the previous one: It could take only 99 (ninety-nine) parameters. The new version could handle 128 parameters, which was sufficient for the immediate needs of the customer, but the design allowed expansion to 256 parameters. If there ever was a case for Fortran COMMON blocks, I would call this a candidate. (Don't take me wrong - I am not suggesting using COMMON blocks as good programming practice. Nor is 100+ function parameters.)
:omg: :wtf: Just thinking about that is probably enough that you need some medication. Have a :beer: on me.
Did you ever see history portrayed as an old man with a wise brow and pulseless heart, waging all things in the balance of reason? Is not rather the genius of history like an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful? --Zachris Topelius Training a telescope on one’s own belly button will only reveal lint. You like that? You go right on staring at it. I prefer looking at galaxies. -- Sarah Hoyt
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcParameters? Why not just use Global Variables??? Wait for it... ROTFLMAO... I did flag this as a JOKE! That is a HORRIBLE IDEA, for the record... And for the record, we used a structure, and it worked beautifully. The tricky part is when you call a function that needs 1 of those parameters... Do you pass the structure, or struct.val3 ? (we based it on the completeness of the function. If we felt it wasn't changing, then we sent as little data as possible, but more than one field meant the structure).
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In the old days, I was working with a Fortran compilers where we had to push the release due to one (important) customer who had run into a limitation of the previous one: It could take only 99 (ninety-nine) parameters. The new version could handle 128 parameters, which was sufficient for the immediate needs of the customer, but the design allowed expansion to 256 parameters. If there ever was a case for Fortran COMMON blocks, I would call this a candidate. (Don't take me wrong - I am not suggesting using COMMON blocks as good programming practice. Nor is 100+ function parameters.)
COMMON is certainly good "programming practice" as long as each COMMON is named and contains a single value. Otherwise I submit that COMMON should be found non-complying in coding standards.
Gus Gustafson
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Key-Value Options: Let's say you have a function that can take a bunch of options for how to build something, say some auto-generated HTML, when passing them as parameters is just too cumbersome? Personally, I would just put all the options into a struct and pass an instance of the struct into the function. The nice thing about that is, the struct (or class, if you wish) documents all the possible options. Now, in the land of Ruby, I see everybody everywhere using key-value pairs associated with symbols, like this:
{option1: true, option2: "foobar", option3: 42}Now of course the symbols usually have some intelligent meaning, but you have absolutely no clue what these optional parameters are unless you look up the online documentation (if it exists) and then can be sprawled across numerous pages on the website. And worse, in the Ruby code, these options are of course usually tested using the symbol:if opts[:option1] ... endsuch that, if you mistype the "key" (symbol), nothing is going to complain to you, unless the programmer checks the option list for unknown options, which I have NEVER seen done. Now, there's lots of alternatives in the, say, C# world. Your function can take a variable number of parameters. You can require that the caller provides a callback for resolving options. You can just put everything into the function's parameter list, and so forth. Or, like Rubyists, you can pass in a dictionary or some such thing of options. Valueless Options (aka flags): So far, the above discussion deals with options that have associated values. There is also the issue of "valueless" options -- if the "key" is present, then the option is "selected." One of the most common ways of passing in valueless options to a function in most languages is of course with an enum, especially when you can use the "or" operator to combine multiple valueless options. Now, mind you, in Ruby, there is no concept of an enum, which is a serious drawback in my opinion. But I'm curious what people consider to be their own best practice. MarcIf the function has "too many" arguments, accept that it's ugly and live with it. Putting them in a struct is just hiding the ugliness and moving the complexity elsewhere, possibly remote from the function call itself. In my mind, it just makes for extra work to understand and maintain. The optional argument example is a perfect time to use an overload. That way you have a place to document the unique behavior of that variation of the function, and have documented for the next developer which arguments need to be specified as a set. The struct solution isn't a bad way to hide the problem, although a polymorphic class might be better depending on the needs.
We can program with only 1's, but if all you've got are zeros, you've got nothing.
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I would have to go with wrapping the parameters in a struct/class. That way, I can put all sorts of validation in there that gives the object some context.
I like that approach. It comes in handy with REST wrappers. You can create a struct that can validate and concatenate either the parameter list that you GET URL will need or the XML that your POST will need in a ToString() like method.
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Dependancy Injection!!
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Except that you have created event arguments for use with none events. The sender is probably going to be completely useless.
You do understand that we are working with event driven programming right? The entire inner working of the object programming model has a point of origin and the event that triggered it. You should always be making your code generic as it can be understood by everything, and your procedure should be tread safe - which means everything you need should be passed as a parameter.
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You do understand that we are working with event driven programming right? The entire inner working of the object programming model has a point of origin and the event that triggered it. You should always be making your code generic as it can be understood by everything, and your procedure should be tread safe - which means everything you need should be passed as a parameter.
Colborne_Greg wrote:
You do understand that we are working with event driven programming right?
That's a very narrow point of view, focused on one technology set. At no stage did Marc state he was asking about an event. And while there is a point of origin, there's no guarantee that he is responding to an event - you may have noticed that Marc was talking in a generic sense, hence the reason he mentioned ROR. So, in the case of doing something like processing a batch input on a file, forcing the programming model to use an event signature doesn't really make sense.
Colborne_Greg wrote:
You should always be making your code generic as it can be understood by everything, and your procedure should be tread safe - which means everything you need should be passed as a parameter.
And that is why my response, at the top of this thread, stated that I would normally wrap things up into an object.
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Colborne_Greg wrote:
You do understand that we are working with event driven programming right?
That's a very narrow point of view, focused on one technology set. At no stage did Marc state he was asking about an event. And while there is a point of origin, there's no guarantee that he is responding to an event - you may have noticed that Marc was talking in a generic sense, hence the reason he mentioned ROR. So, in the case of doing something like processing a batch input on a file, forcing the programming model to use an event signature doesn't really make sense.
Colborne_Greg wrote:
You should always be making your code generic as it can be understood by everything, and your procedure should be tread safe - which means everything you need should be passed as a parameter.
And that is why my response, at the top of this thread, stated that I would normally wrap things up into an object.
When the procedure was called is an event when the processing a batch input on a file BOF reached and EOF reached are events. Everything is an event, and inheriting from eventargs allows your code to be repurposed everywhere, and when all your delegates have the same signature you wont get held back when you want to dive deeper into generics.
