Exposing List<> outside class [modified]

[leppie]

I think your generics got swallowed by the HTML monster! :)

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[Jan Sommer]

You're right - should be working now.

[leppie]

Depending on the usage, Customers could be IEnumerable<Customer>. But I do not see any other way of mutating that list.

Jan Sommer wrote:

I'm asking because my teacher says that the above example is bad OOP

So did he not bother to explain to you why he feels that way? Sounds like a bad teacher to me. Ask him if he is happy with what he does ;P

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[Jan Sommer]

He said he didn't know a better way :P The first solution i came up with was to add this method to class Partner:

public IEnumerator<Customer> GetCustomersEnumerator()
{
return this.cust.GetEnumerator();
}

which is working just fine for retrieving all the customers with this code:

IEnumerator<Customer> alist = partners.GetCustomerEnumerator();

while(alist.MoveNext())
{
Console.WriteLine(alist.Current.someProperty);
}

But in the userinterface, when a user clicks the customer (shown in a listview) i'd like to use the customer-index to retrieve the correct customer and send him to another dialog. Currently i'm only able to access each customers information and i can't pick a specific customer, since i don't have access to the list. Am i doing it all wrong? I was considering using a database which would make everything alot easier, but that would be too hard for the other students (according to my teacher :P)

[leppie]

Jan Sommer wrote:

Am i doing it all wrong?

You have 2 choices: 1. Expose it as an IList<Customer> and do cust.ToArray(). 2. Wrap cust in a ReadOnlyCollection<Customer>. I would prefer the latter.

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[Thomas Weller 0]

Why for heavens sake should this be bad coding practice?? This is the normal way to do it: Declaring a private field and exposing it through a public property. There's no other way to do it right - your teacher is definitely wrong! There is one concern with this I can think of: 1. The list should be immutable. If so, simply use customers.AsReadOnly() in your get accessor and provide some methods like Add/RemoveCustomer in your Partner class. Regards Thomas

www.thomas-weller.de Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
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[Jan Sommer]

Thanks... Didn't know of the ReadOnlyCollection but that seems reasonable to use..

[Alan Balkany]

I tend to agree. The only design guideline this might violate is from Bill Wagner's "Effective C#, Item 23: "Avoid Returning References to Internal Class Objects". But Thomas' suggestion to return a read-only object addresses (no pun intended) this issue.

[Jan Sommer]

i'm glad to hear i'm not completely wrong.. this sure have saved me a headache..

[Thomas Weller 0]

Always at your service... :) Regards Thomas

www.thomas-weller.de Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Programmer - an organism that turns coffee into software.