判断字符串是否为空

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.title=@"判断字符串是否为空";
    
    NSLog(@"--字符串是否为空-%i-",[self isBlankString:@"123455"]);
    
}
//判断字符串是否为空
- (BOOL) isBlankString:(NSString *)string {
    if (string == nil || string == NULL) {
        return YES;
    }
    if ([string isKindOfClass:[NSNull class]]) {
        return YES;
    }
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {
        return YES;
    }
    return NO;
}