{Dev Tricks}

November 23rd, 2008 by valerian

If are familiar to the use of ternary operators, you must have encountered several situations like this one :

string pageTitle = getTitle() ? getTitle() : "Default Title";

Download this code: bad_situation.cs

You would want to call getTitle() only once, but then you wouldn’t have a simple one-lined initialization of you variable.

Actually there is a simple solution that most langages implements, the null coalescing operator; let’s replace the above C# code with this one :

string pageTitle = getTitle() ?? "Default Title";

Download this code: solution.cs

Now you have the same behaviour, but with only one call to your function. The syntax is simple :

possibly_null_value ?? value_if_null

the “??” operator is implemented in C# since C# 2.0.

You also have it in C and C++ as a GNU extension using the “?:” operator :

string pageTitle = getTitle() ?: "Default Title";

Download this code: solution.cpp

You can get the same behaviour in javascript using the “||” operator :

pageTitle = getTitle() || "Default Title";

Download this code: solution.js

You can read more about this operator here and here

This entry was posted on Sunday, November 23rd, 2008 at 6:01 pm and is filed under Code. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.