如何将字符串附加到NSMutableString

Question

我是Objective-c的绝对新手

用这个代码

NSMutableString *teststring;
[teststring appendString:@"hey"];
NSLog(teststring);

控制台中没有显示任何内容.

当然我在这里做错了...... :-)

Answer 1

您需要先创建字符串.

NSMutableString *teststring = [[NSMutableString alloc]init];

[teststring appendString:@"hey"];

NSLog(teststring);

现在,它将打印出来.

Answer 2

将第一行更改为

NSMutableString *teststring = [NSMutableString string];

Answer 3

这条线

NSMutableString *teststring;

只是建立一个指针,但不创建任何东西.相反,您需要创建一个新实例NSMutableString,例如:

NSMutableString *teststring = [[NSMutableString alloc] init];
[teststring appendString:@"hey"];
NSLog("%@", teststring);

Answer 4

样本：

NSMutableString *buffer = [[NSMutableString alloc] init]; // retain count = 1. Because of the "alloc", you have to call a release later

[buffer appendString:@"abc"];
NSLog(@"1 : %@", buffer);
[buffer appendString:@"def"];
NSLog(@"2 : %@", buffer);

[buffer release]; // retain count = 0 => delete object from memory