[英]JSONKit: changing and serializing JSON attribute's value
I am using JSONKit to parse JSON string into NSDictionary: 我正在使用JSONKit将JSON字符串解析为NSDictionary:
NSDictionary *deserializedData = [jsonString objectFromJSONString];
My question is: how can I change the dictionary values and get a changed JSON String? 我的问题是:如何更改字典值并获取更改的JSON字符串?
I've tried to change the dictionary values: 我试图更改字典值:
[deserializedData setObject:[NSNumber numberWithInt:iRatings] forKey:@"ratings"];
But the app crashes in that line. 但是该应用程序在该行崩溃。 What am I doing wrong?
我究竟做错了什么?
Thanks in advance! 提前致谢!
While the other answers are correct, what you really want in this case is: 尽管其他答案是正确的,但在这种情况下,您真正想要的是:
NSMutableDictionary *deserializedData = [jsonString mutableObjectFromJSONString];
The mutableObjectFromJSONString
method will create a mutable dictionary directly, which saves time and memory. mutableObjectFromJSONString
方法将直接创建一个可变字典,从而节省时间和内存。
//
// we begin with our string in json format
//
NSString *jsonString = [[NSString alloc] initWithString:@"{\"1\":\"Hole 1: Rossy Robinson - $25\",\"2\":\"Hole 7: Davey Ambrose - $25\",\"3\":\"Hole 14: Ross Robinson - $25\"}"];
//
// convert the json string to an NSMutableDictionary
//
NSError *e;
NSMutableDictionary *JSONdic = [NSJSONSerialization JSONObjectWithData: [jsonString dataUsingEncoding: NSUTF8StringEncoding] options: NSJSONReadingMutableContainers error: &e];
//
// change a value and add a new value in the dict
//
NSLog(@"before: object for key 1 is: %@", [JSONdic objectForKey:@"1"]);
[JSONdic setObject:@"xxx" forKey:@"1"];
[JSONdic setObject:@"Phil McQuitty" forKey:@"2"];
//
//convert dictionary object to json data
//
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:JSONdic options:NSJSONWritingPrettyPrinted error:&e];
//
// convert the json data back to a string
//
NSString *jsonText = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];\
//
// print out the final results
//
NSLog(@"back to string: %@", jsonText);
NSDictionary
is an immutable dictionary, you need NSMutableDictionary
to change the data. NSDictionary
是一个不可变的字典,您需要NSMutableDictionary
来更改数据。 I'm not sure about JSONKit, but the built-in Cocoa JSON parser has a flag to return the data in mutable containers. 我不确定JSONKit,但是内置的Cocoa JSON解析器有一个标志来返回可变容器中的数据。
In worst case, you can do something like that: 在最坏的情况下,您可以执行以下操作:
NSMutableDictionary* data = [NSMutableDictionary dictionaryWithDictionary:[jsonString objectFromJSONString]];
[data setObject:[NSNumber numberWithInt:iRatings] forKey:@"ratings"];
You try to change an immutableobject. 您尝试更改一个不可变的对象。
NSMutableDictionary *deserializedData = [NSMutableDictionary dictionaryWithDictionary: [jsonString objectFromJSONString]];
This is a mutable dictionary and you can change the values in it. 这是一个可变的字典,您可以更改其中的值。
You try like this: 您可以这样尝试:
NSMutableDictionary *deserializedData = [NSMutableDictionary dictionaryWithDictionary: [jsonString objectFromJSONString]];
and then change the values: 然后更改值:
[deserializedData setObject:[NSNumber numberWithInt:iRatings] forKey:@"ratings"];
For NSDictionary
we cannot add or change values, thats why application is crashing. 对于
NSDictionary
我们无法添加或更改值,这就是应用程序崩溃的原因。
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