iOS 使用系统API获取 字符串的 size

NSString *string1 = @"helloworld";
    CGSize fontSize = [string1 sizeWithAttributes:@{NSFontAttributeName : [UIFont systemFontOfSize:15]}];
    
    NSLog(@"the fontSize is %@", NSStringFromCGSize(testSize));
    
    NSLog(@"the testSize is %@", NSStringFromCGSize(testSize));