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I want to clarify whether different instances of an Objective-C class share static variables that occur inside methods, or if each instance gets its own copy:
- (void) myMethod { static int myVar = 0; } 
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Static variables are shared among all instances of a class. Non static variables are specific to that instance of a class. Static variable is like a global variable and is available to all methods. Non static variable is like a local variable and they can be accessed through only instance of a class.
3. The static Fields (or Class Variables) In Java, when we declare a field static, exactly a single copy of that field is created and shared among all instances of that class.
Class Variables and MethodsA static variable is shared by all instances of a class. Only one variable created for the class.
Each thread will share the same static variable which is mostly likely a global variable.
Static locals are shared between method calls AND instances. You can think of them as globals which are visible only inside their methods:
- (void) showVars { int i = 0; static int j = 0; i++; j++; NSLog(@"i = %i ; j = %i", i, j); } [...]
[obj1 showVars]; [obj2 showVars]; [obj1 showVars]; [obj2 showVars]; Above calls on 2 different instances will output:
i = 1 ; j = 1 i = 1 ; j = 2 i = 1 ; j = 3 i = 1 ; j = 4 It's the same as a static variable in C; the instances will share the variable. If you want each instance to have its own copy, you want an instance variable (declared in the @interface block).
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