将字符索引分配给字符索引

Question

[a characterAtIndex:0] = [b characterAtIndex:0]; 

我想要分配字符a字符b。

但失败了，怎么样？

Answer 1

NSMutableString *a = [NSMutableString stringWithString:@"HOUSE" ]; 

    NSString *b= @"MUSIC"; 

[a replaceCharactersInRange:NSMakeRange(0, 1) withString:[b substringWithRange:NSMakeRange(0, 1)]]; 

当你得到一个结果MOUSE ;-)

Answer 2

如果你正在寻找的方法是这样的：setCharacter:atIndex:

然后看下面的代码：

NSMutableString *string=[NSMutableString stringWithString:@"abcdefgh"]; 

[string setCharacter:'X' atIndex:0]; //Note X is character not string so "X" and its is primitive therefore even @ is not prefixed. 

NSLog(@"%@",string); 

这通过NSMutableString的类别获得，其方法实施

@implementation NSMutableString (SetCharacterAtIndex) 

- (void)setCharacter:(char)character atIndex:(NSUInteger)index;{ 

    [self replaceCharactersInRange:NSMakeRange(index, 1) withString:[NSString stringWithFormat:@"%c",character]]; 

} 

编辑：

具有上述方法之后，可以使用：

[一个characterAtIndex：0] = [B characterAtIndex：0];

[a setCharacter:[b characterAtIndex:0] atIndex:0];