Meaning of IOS __attribute__ ((Warn_unused_result))

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The meaning of this keyword: If a function uses this keyword, then when the function is called, it checks or uses the return value, and a compiler warns.

Use case: When the function is encapsulated (or the SDK is written), if the use of the return value is more important, then use this keyword to remind the compiler to check whether the return value is being exploited.

Example:

-(BOOL) TestFunc: (nsinteger) num __attribute__ ((warn_unused_result)) {    return num > 0? Yes:no;}

If I call this

    [Self testfunc:10];

The compiler will warn you as follows

After checking the return value, the warning disappears

BOOL result =  [self testfunc:10];

Meaning of IOS __attribute__ ((Warn_unused_result))