NSMutableArray到JSON对象

Question

我有一个方法，我想返回一个NSData对象或一个'NSString'，它必须是格式的JSON对象。

目前这是我的;

-(NSData *)JSONData{ 

    NSMutableArray* arr = [NSMutableArray array]; 
    for (int j = 0; j < self.sales.subArray.count; j++) 
    { 
     SalesObject* subCategory = [self.sales.subArray objectAtIndex:j]; 


     NSDictionary * dict =[NSDictionary dictionaryWithObjectsAndKeys: 
           @"category_id",subCategory.category_id, 
           @"discounted",@"0", 
           @"price",subCategory.price, 
           @"active",subCategory.isActive, nil]; 
     NSLog(@"Dict %@",dict); 

     [arr addObject:dict]; 

    } 

    NSLog(@"Arr %@",arr); 

    NSLog(@"Arr %@",arr); 

    NSString *string = [arr description]; 
    NSData * jsonData = [NSJSONSerialization dataWithJSONObject:string options:kNilOptions error:nil]; 
    NSLog(@"JSON Data %@",jsonData); 

    return jsonData; 
} 

正如你可以看到我尝试了NSMutableArray转换为NSData对象，但它没有工作。我得到;

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid (non-string) key in JSON dictionary' 

我现在碰到下面的错误;

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[NSJSONSerialization dataWithJSONObject:options:error:]: Invalid top-level type in JSON write' 

Answer 1

您处于正确的轨道上，但您已将您的键/值对颠倒过来。代替使用新的目标C辞典文字语法，这是更短和更容易阅读，并且因此更容易发现错误：

NSDictionary *dict = @{ 
    @"category_id" : subCategory.category_id, 
    @"discounted" : @"0",  // Should that be @(0) ??? 
    @"price"  : subCategory.price, 
    @"active"  : subCategory.isActive 
}; 

EDIT附加问题涉及使用该阵列的描述（即字符串），而不是数组本身，用于创建JSON数据。它应该是：

NSError *error = nil; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:arr 
                options:kNilOptions 
                error:&error]; 
if (!jsonData) { 
    NSLog(@"Achtung! Failed to create JSON data: %@", [error localizedDescription]); 
} 

Answer 2

更改字典的定义从

NSDictionary * dict =[NSDictionary dictionaryWithObjectsAndKeys: 
          @"category_id",subCategory.category_id, 
          @"discounted",@"0", 
          @"price",subCategory.price, 
          @"active",subCategory.isActive, nil]; 

到

NSDictionary * dict =[NSDictionary dictionaryWithObjectsAndKeys: 
          subCategory.category_id,@"category_id", 
          @"0", @"discounted", 
          subCategory.price,@"price", 
          subCategory.isActive, @"active", nil];