如何在目标C中将类对象转换为JSON字符串

问题描述：

1.我创建了类对象，然后使用此代码将值添加到我的类中

1.I create class objects then add value to my class with this code

csJastorPollQuestion *pq = [[csJastorPollQuestion alloc] initWithID:@"01" Name:@"AAA"];

2.我在存在的NSLog中显示了"csJastorPollQuestion"

2.I shown "csJastorPollQuestion" in NSLog it's present

#<csJastorPollQuestion: id = (null) { ID = 01; Name = AAA; }>

3.我使用此代码将"csJastorPollQuestion"转换为json字符串

3.I convert "csJastorPollQuestion" to json string with this code

NSData *jsd = [NSJSONSerialization dataWithJSONObject:pq options:NSJSONWritingPrettyPrinted error:&er];
NSString *jsonString = [[NSString alloc] initWithData:jsd encoding:NSUTF8StringEncoding];

4.运行项目时，显示为错误

4.When I run my project it's shown error this

[NSJSONSerialization dataWithJSONObject:options:error:]: Invalid top-level type in JSON write'

5.将"csJastorPollQuestion"转换为json字符串的正确方法是什么?

5.What is the right way for convert "csJastorPollQuestion" to json string?

答

dataWithJSONObject:options:error:方法仅适用于NSJSONSerialization知道如何转换为JSON的对象.这意味着:

The dataWithJSONObject:options:error: method only works on objects that NSJSONSerialization knows how to convert to JSON. That means:

顶级对象必须是NSArray或NSDictionary
包含的对象必须是NSString，NSNumber，NSArray，NSDictionary或NSNull的实例.
字典键必须为NSString s
数字不能为无限或NaN.

The top-level object must be an NSArray or NSDictionary
Objects contained must be instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
Dictionary keys must be NSStrings
Numbers must not be infinite or NaN.

您需要转换为字典或数组表示形式才能使用此方法.

You need to convert to a dictionary or array representation to use this method.

如何在目标C中将类对象转换为JSON字符串

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