(nonatomic) NSString *string; @property (nonatomic, copy) NSString *copiedString; @end // MyClass.m @implementation MyClass - (void)someFunction { SomeModel *model = [[SomeModel alloc] init]; NSMutableString *baseString = [NSMutableString stringWithString:@"111"]; model.string = baseString; model.copiedString = baseString; [baseString appendString:@"!!!"]; NSLog(@"string : %@", con.string); //結果:111!!! NSLog(@"copied string : %@", con.copiedString); //結果:111 } @end