A simple way
NSLog(@"padding space:%@",[NSString stringWithFormat:@"AA%6d",123]);
NSLog(@"padding zero:%@",[NSString stringWithFormat:@"AA%06d",123]);
//padding space:AA 123
//padding zero :AA000213
以上方式只能補空白或是0，如果要補其它字元呢?
NSNumberFormatter *formatter = [NSNumberFormatter new];
[formatter setPaddingPosition:NSNumberFormatterPadBeforePrefix];
[formatter setPaddingCharacter:@"="];
[formatter setFormatWidth:6];
NSLog(@"%@", [NSString stringWithFormat:@"AA%@", [formatter stringFromNumber:@123]]);
//padding equals:AA===123
