Objective-C JSON操作

Objective-C
操作JSON 主要使用的是 NSJSONSerialization
这个类

NSJSONSerialization
包含了以下五个类函数

+
(BOOL)isValidJSONObject:(id)obj;

判断
该实例(obj)是否为JSONObject

需满足下面三个条件

1.obj
是NSArray 或 NSDictionay 以及他们派生出来的子类

2.obj
包含的所有对象是NSString,NSNumber,NSArray,NSDictionary 或NSNull

3.NSNumber的对象不能是NaN或无穷大

+
(NSData *)dataWithJSONObject:(id)obj
options:(NSJSONWritingOptions)opt error:(NSError
**)error;

将JSONObject的实例转成NSData

+
(id)JSONObjectWithData:(NSData *)data
options:(NSJSONReadingOptions)opt error:(NSError
**)error;

将NSData类型的实例转成JSONObject

+
(NSInteger)writeJSONObject:(id)obj toStream:(NSOutputStream
*)stream options:(NSJSONWritingOptions)opt error:(NSError
**)error;

将一个JSONObject的实例写入到一个输出流中
返回写入的长度

+
(id)JSONObjectWithStream:(NSInputStream *)stream
options:(NSJSONReadingOptions)opt error:(NSError
**)error;

从输入流中读取成JSONObject
并返回

代码演示:

Objective-c代码

JSON操作" />

NSMutableDictionary *dictionary = [[NSMutableDictionary alloc]init];

[dictionary setValue:@"xiaominfc" forKey:@"username"];

[dictionary setValue:@"1991-03-26" forKey:@"birthday"];

[dictionary setValue:[NSNumber numberWithInteger:23] forKey:@"age"];

NSArray *arrayOfAnthonysChildren = [[NSArray alloc]initWithObjects:@"Java",@"Objective-C",@"Python",@"C++", nil];

[dictionary setValue:arrayOfAnthonysChildren forKey:@"program_language"];

if([NSJSONSerialization isValidJSONObject:dictionary]){

NSLog(@"it is a JSONObject!");

}

//use dataWithJSONObject fun

NSError *error = nil;

NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error];

if([jsonData length] > 0 && error == nil) {

NSString *jsonString = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];

NSLog(@"data:%@",jsonString);

}

//use JSONObjectWithData fun

NSString *jsonDataString = @"{"username":"xiaominfc","city":"深圳"}";

NSData *data = [jsonDataString dataUsingEncoding:NSUTF8StringEncoding];

id jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];

if ([jsonObject isKindOfClass:[NSDictionary class]]) {

NSDictionary *jsonDictionary = (NSDictionary*)jsonObject;

NSLog(@"username:%@ And city:%@",[jsonDictionary valueForKey:@"username"],[jsonDictionary valueForKey:@"city"]);

}

//use writeJSONObject fun

NSString *filePath = @"/Users/xiaominfc/text.txt";

NSOutputStream *outStream = [[NSOutputStream alloc]initToFileAtPath:filePath append:NO];

[outStream open];

NSInteger length = [NSJSONSerialization writeJSONObject:dictionary toStream:outStream options:NSJSONWritingPrettyPrinted error:&error];

NSLog(@"write %ld bytes",(long)length);

[outStream close];

//use JSONObjectWithStream

NSInputStream *inStream = [[NSInputStream alloc]initWithFileAtPath:filePath];

[inStream open];

id streamObject = [NSJSONSerialization JSONObjectWithStream:inStream options:NSJSONReadingAllowFragments error:&error];

if ([streamObject isKindOfClass:[NSDictionary class]]) {

NSDictionary *jsonDictionary = (NSDictionary*)streamObject;

NSNumber *ageNumber = (NSNumber*)[jsonDictionary valueForKey:@"age"];

NSLog(@"username:%@ And age:%d",[jsonDictionary valueForKey:@"username"],[ageNumber intValue]);

}

[inStream close];