Static member functions are used in xcode to replace global variables.

Objective C supports global variables in the same usage as C/C ++. However, when the following requirements are met: for example, variables defined in Class A can be accessed and modified without creating an instance of Class A in Class B. It is not appropriate to use global variables. In this case, we need to define a static variable in the implementation file of Class A, and then define a static member function (class method) for Class A to operate on the variable. In this way, you do not need to create a class A instance to access static variables in other classes. Although this static variable is not a static member variable of Class A, it achieves the same effect. The key to not defining global variables is the scope of variables. The scope of static variables is limited to a single file. Code// Example. h @ interface Example: nsobject {}-(ID) Init; + (INT) instancecount; @ end copy the code // example. M # import "example. H "static int count; @ implementation example-(ID) Init {self = [Super init]; If (nil! = Self) {count + = 1;} return self;} + (INT) instancecount {return count ;} @ end copy code in the above example, you can use [Example instancecount] to access the static variable count without creating an instance.