字符串

+ (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;
    
}

数组

if (array != nil && ![array isKindOfClass:[NSNull class]] && array.count != 0)

字典

[Dict isKindOfClass:[NSNull class]] 或者 [value isEqual:[NSNull null]]

// 或者 写分类
if(![dict objectForKey:key]){  
    return NO;  
}  
      
id obj = [dict objectForKey:key];// judge NSNull  
      
return ![obj isEqual:[NSNull null]];