NSMutableString *copyMutableString = [mutableCopyString copy];

[zhangxueyang]

NSString *string = @"测试数据";
NSString *copyString = [string copy]；
NSMutableString *mutableCopyString = [string mutableCopy];
NSMutableString *copyMutableString = [string copy];
NSLog(@"%p,%p,%p,%p", string, copyString, mutableCopyString, copyMutableString);

第三行改一下 严谨一点

NSString *string = @"测试数据";
NSString *copyString = [string copy]；
NSMutableString *mutableCopyString = [string mutableCopy];
NSMutableString *copyMutableString = [mutableCopyString copy];
NSLog(@"%p,%p,%p,%p", string, copyString, mutableCopyString, copyMutableString);