您可以将变量设为公开，或者将其变成属性。例如，将其公开：

You can either make the variable public, or make it into a property. For example, to make it public:

@interface Class1
{
@public
    int var;
}
// methods...
@end

// Inside a Class2 method:
Class1 *obj = ...;
obj->var = 3;

要使其成为属性：

@interface Class1
{
    int var;  // @protected by default
}
@property (readwrite, nonatomic) int var;
// methods...
@end

@implementation Class1
@synthesize var;
...
@end

// Inside a Class2 method:
Class1 *obj = ...;
obj.var = 3;  // implicitly calls [obj setVar:3]
int x = obj.var;  // implicitly calls x = [obj var];