什么是使用条件运算符的其他什么都不做？

Question

I want to know what is the equivalent of this if statement:

if (condition) {
        // do something
    }else{
        // do nothing

    }

Using the conditional operator:

(condition) ? // [do nothing] : {do nothing} "

Answer 1

It's not possible to "do nothing" using the conditional operator. You always have to have valid expressions on both sides, although both expressions can be casted to void .

Answer 2

This is one of the dis-advantage of ternary operator ( ?: ).

It needs expressions in all the three places. You cant skip any of them.

You can do some tweak on it, however its True-part and / or False-part can be assigned to the same as :

int big=100;
big= (10 > 100) ? 0 : big;

Answer 3

if (!condition) {
        // do something
    }else{
        // do nothing

    }

Take a look at the !before contition now :-)

The ! before the condition just switches the "if", to "if not"...

Is that what you have been searching for?

Answer 4

originalValue = (condition) ? newValue : originalValue

The compiler should then remove the unnecessary assign of originalValue to itself.

GCC had an extension to do give you something more to what you where looking for, something like

originalValue = condition ?: newValue;

So it may be available in clang also. You would have to ! the condition though.

Answer 5

In normal code the answer is there is no equivalent - all sub expressions of an expression must have a value, but...

the following is not a recommendation

Something along the lines of the following should work in the general case:

condition ? ( (^{ do something })(), 0 ) : 0;

That is for the general case. If do something is a single, non-compound, statement; such as a method call; then the block can be dropped to give:

condition ? (do something, 0) : 0;

Again this is NOT recommended in real code!

Answer 6

你可以做这样的事情

someBool ? [self someFunction] : (^{})(); //empty block