如何使用 Objective-C 解析 JSON？

Don't reinvent the wheel. Use Json 框架 or something similar.

If you do decide to use json-framework, here's how you would parse a JSON string into an NSDictionary:

SBJsonParser* parser = [[[SBJsonParser alloc] init] autorelease];
// assuming jsonString is your JSON string...
NSDictionary* myDict = [parser objectWithString:jsonString];


// now you can grab data out of the dictionary using objectForKey or another dictionary method

1. 我推荐并使用 触摸 JSON解析 JSON。

2. 回答你对 Alex 的评论。这里有一些快速代码，可以让您从返回的 json 字典中获得 activity _ Details、 last _ name 等字段:

   NSDictionary *userinfo=[jsondic valueforKey:@"#data"];
   NSDictionary *user;
   NSInteger i = 0;
   NSString *skey;
   if(userinfo != nil){
   for( i = 0; i < [userinfo count]; i++ ) {
   if(i)
   skey = [NSString stringWithFormat:@"%d",i];
   else
   skey = @"";
   
   
   user = [userinfo objectForKey:skey];
   NSLog(@"activity_details:%@",[user objectForKey:@"activity_details"]);
   NSLog(@"last_name:%@",[user objectForKey:@"last_name"]);
   NSLog(@"first_name:%@",[user objectForKey:@"first_name"]);
   NSLog(@"photo_url:%@",[user objectForKey:@"photo_url"]);
   }
   }
   

从 OS X v10.7和 iOS 5发布的角度来看，现在最值得推荐的可能是苹果提供的 JSON 解析器 NSJSONSerialization。只有在发现第三方选项在运行时不可用时才使用该选项作为备用选项。

So, for example:

NSData *returnedData = ...JSON data, probably from a web request...


// probably check here that returnedData isn't nil; attempting
// NSJSONSerialization with nil data raises an exception, and who
// knows how your third-party library intends to react?


if(NSClassFromString(@"NSJSONSerialization"))
{
NSError *error = nil;
id object = [NSJSONSerialization
JSONObjectWithData:returnedData
options:0
error:&error];


if(error) { /* JSON was malformed, act appropriately here */ }


// the originating poster wants to deal with dictionaries;
// assuming you do too then something like this is the first
// validation step:
if([object isKindOfClass:[NSDictionary class]])
{
NSDictionary *results = object;
/* proceed with results as you like; the assignment to
an explicit NSDictionary * is artificial step to get
compile-time checking from here on down (and better autocompletion
when editing). You could have just made object an NSDictionary *
in the first place but stylistically you might prefer to keep
the question of type open until it's confirmed */
}
else
{
/* there's no guarantee that the outermost object in a JSON
packet will be a dictionary; if we get here then it wasn't,
so 'object' shouldn't be treated as an NSDictionary; probably
you need to report a suitable error condition */
}
}
else
{
// the user is using iOS 4; we'll need to use a third-party solution.
// If you don't intend to support iOS 4 then get rid of this entire
// conditional and just jump straight to
// NSError *error = nil;
// [NSJSONSerialization JSONObjectWithData:...
}

NSString* path  = [[NSBundle mainBundle] pathForResource:@"index" ofType:@"json"];


//将文件内容读取到字符串中，注意编码NSUTF8StringEncoding 防止乱码，
NSString* jsonString = [[NSString alloc] initWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];


//将字符串写到缓冲区。
NSData* jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];


NSError *jsonError;
id allKeys = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONWritingPrettyPrinted error:&jsonError];




for (int i=0; i<[allKeys count]; i++) {
NSDictionary *arrayResult = [allKeys objectAtIndex:i];
NSLog(@"name=%@",[arrayResult objectForKey:@"storyboardName"]);


}

文件:

 [
{
"ID":1,
"idSort" : 0,
"deleted":0,
"storyboardName" : "MLMember",
"dispalyTitle" : "76.360779",
"rightLevel" : "10.010490",
"showTabBar" : 1,
"openWeb" : 0,
"webUrl":""
},
{
"ID":1,
"idSort" : 0,
"deleted":0,
"storyboardName" : "0.00",
"dispalyTitle" : "76.360779",
"rightLevel" : "10.010490",
"showTabBar" : 1,
"openWeb" : 0,
"webUrl":""
}
]

使用 NSJSONSerialization 的 JSON 解析

   NSString* path  = [[NSBundle mainBundle] pathForResource:@"data" ofType:@"json"];
   

//Here you can take JSON string from your URL ,I am using json file
NSString* jsonString = [[NSString alloc] initWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];
NSData* jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *jsonError;
NSArray *jsonDataArray = [NSJSONSerialization JSONObjectWithData:[jsonString dataUsingEncoding:NSUTF8StringEncoding] options:kNilOptions error:&jsonError];
  

NSLog(@"jsonDataArray: %@",jsonDataArray);


NSDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&jsonError];
if(jsonObject !=nil){
// NSString *errorCode=[NSMutableString stringWithFormat:@"%@",[jsonObject objectForKey:@"response"]];
   

        

if(![[jsonObject objectForKey:@"#data"] isEqual:@""]){
            

NSMutableArray *array=[jsonObject objectForKey:@"#data"];
// NSLog(@"array: %@",array);
NSLog(@"array: %d",array.count);
            

int k = 0;
for(int z = 0; z<array.count;z++){
                

NSString *strfd = [NSString stringWithFormat:@"%d",k];
NSDictionary *dicr = jsonObject[@"#data"][strfd];
k=k+1;
// NSLog(@"dicr: %@",dicr);
NSLog(@"Firstname - Lastname   : %@ - %@",
[NSMutableString stringWithFormat:@"%@",[dicr objectForKey:@"user_first_name"]],
[NSMutableString stringWithFormat:@"%@",[dicr objectForKey:@"user_last_name"]]);
}
            

}


}

您可以看到控制台的输出如下:

名-姓: Chandra Bhusan-Pandey

名-姓: Kalaiyarasan-Balu

Firstname-Lastname: (null)-(null)

名-姓: Girija-S

名-姓: Girija-S

Firstname-Lastname: (null)-(null)