如果它总是使用相同的字符：

If it is always the same character you can use:

stringByReplacingOccurrencesOfString:withString:

如果它是同一位置的相同字符串，您可以使用：

If it is the same string in the same location you can use:

stringByReplacingOccurrencesOfString:withString:options:range:

如果只是一个特定的位置，你可以使用：

If is just a specific location you can use:

stringByReplacingCharactersInRange:withString:

此处的文档：
https://developer.apple.com/documentati on / foundation / nsstring

例如：

NSString *someText = @"Goat";
NSRange range = NSMakeRange(0,1);
NSString *newText = [someText stringByReplacingCharactersInRange:range withString:@"B"];

newText等于Boat

newText would equal "Boat"