Fave Operator of the Day

Nish Nishant

Jim Crafton wrote:

You tease - don't blue-ball us, give up an example!!!

return _cachedItem ?? (_cachedItem = GetItem());

Regards, Nish

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Jim Crafton

Is this just a C# thing or is there a VB equivalent (I'm almost afraid to ask what that monstrosity would look like)?

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Nish Nishant

Jim Crafton wrote:

Is this just a C# thing or is there a VB equivalent (I'm almost afraid to ask what that monstrosity would look like)?

I don't think there's a VB equivalent (though I don't know for sure).

Regards, Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
My latest book : C++/CLI in Action / Amazon.com link

Shog9 0

Personally, i'd have preferred something along the lines of the GNU C "shortcut ternary" operator (which it closely resembles). But then, i'd have liked it if C# interpreted null values as false instead of requiring an explicit comparison... :->

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...the wind blows over it and it is gone, and its place remembers it no more...

Shog9 0

Jim Crafton wrote:

Is this just a C# thing or is there a VB equivalent (I'm almost afraid to ask what that monstrosity would look like)?

Monstrosity you say? In VB? Unthinkable! :rolleyes: Classic VB (and VB.NET) has a ternary operator... except, it isn't really an operator. The IIF() function takes three operands, if the first is true it returns the second, otherwise it returns the third. Unlike the C++/C# ternary operator, this will always evaluate all three expressions (being a function call rather than an operator, it has to). This provided yet another pitfall when using VB, as expressions such as: someVar = IIF(boolVar, HorriblyDestructiveCall1(), EvenMoreDestructiveCall()) ...would end up trashing whatever global state you were manipulating with the two functions twice, once for each call (remember, this is VB - of course there's a horrible, fragile, global state of some sort). VB9 now provides a true ternary operator - If. So you can write: someVar = If(boolVar, HorriblyDestructiveCall1(), EvenMoreDestructiveCall()) ... and only one of the possible functions will be called. Or, for the null coalescing version: someVar = If(possiblyNothing, BetterThanNothing()) Good times...

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...the wind blows over it and it is gone, and its place remembers it no more...

Christian Graus

Yeah, I love that one.

Christian Graus - Microsoft MVP - C++ "also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )

Christian Graus

yeah, I still from time to time type if (myobj) and then remember.

Christian Graus - Microsoft MVP - C++ "also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )

NormDroid

Jim Crafton wrote:

is there a VB equivalent

Who cares ;)

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M dHatter

NERDS! :cool:

leppie

jmp Allows you to jump from function to function :)

xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach."

leppie

I would have like a ??= operator too, for exactly what you are showing. Personally, I find it more handy with dealing with optionals.

xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach."

Mustafa Ismail Mustafa

and proud! :cool:

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Steve Hansen

Also easy when working with strings. string result = someString ?? string.Empty;

Howard Richards

Aha.. so when is CodeProject being upgrade to 3.5 then ? ;)

'Howard

Pete OHanlon

For the really nerdy:

string value = value1 ?? value2 ?? value3 ?? finalDefaultValue;

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Gary Wheeler

OK. For us poor, ignorant C++ jocks, please explain what that abomination does. I'm guessing it's something like this:

if (value1 != NULL) value = value1;
else if (value2 != NULL) value = value2;
else if (value3 != NULL) value = value3;
else value = finalDefaultValue;

Software Zen: delete this;

Pete OHanlon

Yup - that's exactly what it does - it coalesces through the chain until it finds a none-null value.

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Gary Wheeler

I'm curious. Does this pattern occur often enough in .NET programming that it was worth adding an operator for it? Or is it the case that, since the operator is available, you use that pattern more often?

Software Zen: delete this;

Daniel Grunwald

I use ?? from time to time, but I needed more than a single ?? in an expression. I think a "?." operator would be much more useful than ??. "obj?.Method()" could be syntax sugar for "(obj != null) ? obj.Method() : null" (except that "obj" is evaluated only once). Hopefully MS will add something like that to C# 4.0...

Rocky Moore

Gary Wheeler wrote:

Does this pattern occur often enough in .NET

In normal code, there is often times you want to get a value back, even if it is a specific default value rather than having to deal with nulls. Now that there is nullable types, it happens quite a bit more. While I am not sure that there is a need for a chain of values as mentioned in the prior post, the ?? is handy to have around.

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