objective-c: Functions and static keyword

Functions

function is a concept for C programming language, objective-c is entirely relies on C.

To define a function, you need provide four components: return value, function name, parameters and code block.

like this:

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int getRandomInteger(int minimum, int maximum) { return arc4random_uniform((maximum - minimum) + 1) + minimum; }

the return value is a integer value, function name is getRandownInteger, there are two paramters: minimum and maximum, code block is enclosed by braces.

Function also can use pointer reference as return value or paramaters, like this:

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NSString *getRandomMake(NSArray *makes) {     int maximum = (int)[makes count];     int randomIndex = arc4random_uniform(maximum);     return makes[randomIndex]; }

The declaration and implementation can be sepearted, the declaration tells the compiler that these is a function and the implementation do the real work.

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// Declaration NSString *getRandomMake(NSArray *); // Implementation NSString *getRandomMake(NSArray *makes) {     int maximum = (int)[makes count];     int randomIndex = arc4random_uniform(maximum);     return makes[randomIndex]; }

If a method want call function , the function declaration should be defined before the method.

static word

static functions

By default, all functions have a global scope, if you want limit the function’s scope to the current file, use ‘static’ keyword:

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// Static function declaration static int getRandomInteger(int, int); // Static function implementation static int getRandomInteger(int minimum, int maximum) {     return arc4random_uniform((maximum - minimum) + 1) + minimum; }

Note that static keyword should be use on both the function declaration and implementation.

static local variable

By defualt, the local variable in a function will be reset each time the function is called. If you use ‘static’ midifier on a local variable in a function , the variable value will be remembered.

Note that the local variable’s scope do not changed, it still only accessible inside the function itself.