爲什麼只有當我使用mutableCopy

Question

這NSMutableAttributedString的addAttribute工作，我有以下代碼：

NSMutableAttributedString *attrS = [[NSMutableAttributedString alloc] initWithString:@"• Get Tested Son"]; 
NSMutableAttributedString *boldS = [[NSMutableAttributedString alloc] initWithString:@"Son"]; 

[boldS addAttribute:NSFontAttributeName value:SOMEBOLDFONT range:NSMakeRange(0, boldS.length)]; 

[attrS replaceCharactersInRange:[attrS.string rangeOfString:boldS.string] 
      withAttributedString:boldS]; 

正如你所看到的，我想大膽的Son部分。

[[attrS mutableCopy] replaceCharactersInRange:[attrS.string rangeOfString:boldS.string] 
         withAttributedString:boldS]; 

什麼可能是其中的原因：如果我做上述表述的，但只有工作，如果我這樣做不行？

Answer 1

addAttribute不管你是否拿mutableCopy。你的問題是基於一個錯誤的假設。因此它沒有答案。

運行以下命令：

NSMutableAttributedString *attrS = [[NSMutableAttributedString alloc] initWithString:@"• Get Tested Son"]; 
NSMutableAttributedString *boldS = [[NSMutableAttributedString alloc] initWithString:@"Son"]; 

UIFont *someBoldFont = [UIFont fontWithName:@"Arial" size:23.0f]; 
[boldS addAttribute:NSFontAttributeName value:someBoldFont range:NSMakeRange(0, boldS.length)]; 

NSMutableAttributedString *attrSCopy = [attrS mutableCopy]; 

[attrS replaceCharactersInRange:[attrS.string rangeOfString:boldS.string] 
      withAttributedString:boldS]; 
[attrSCopy replaceCharactersInRange:[attrS.string rangeOfString:boldS.string] 
      withAttributedString:boldS]; 

NSLog(@"%@", [attrS isEqual:attrSCopy] ? @"equal" : @"different"); 

它將輸出equal。將replaceCharactersInRange:註釋爲attrS或attrSCopy，它將輸出different。