Question

I want to convert personArray to a JSON string, and send a request to the server.

I tried something like the following code:

@interface Person : NSObject {
    NSString *name;
    int registered;
}
+ (NSMutableArray *) select;

NSMutableArray *personArray = [Person select]; 


NSString *json = @"{ \"";//TODO

for (int i =0 ;i < [personArray count]; i++) {
    Person *temp = [Person objectAtIndex:i];

    [json stringByAppendingFormat:[NSString stringWithFormat:@"\"name\": \"%@\"", temp.name]
}
json = [json stringByAppendingFormat:[NSString stringWithFormat:@"} \""]];

ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
[request setPostValue:[global userID] forKey:@"user_id"];
[request setPostValue:json forKey:@"json_key"];
[request addRequestHeader:@"Content-type" value:@"application/json"]; 

[request startSynchronous];

The server receives the following data:

{ \"\"name\": \"Tom\"}

The server code is this:

$json = $_POST['json_key'];
echo $json;
$json = json_decode($json, true);
echo $json; // prints nothing

Is there any way to remove the slash, or a prettier solution for converting the object to JSON?

Answer 1

To be sure that the JSON representation is being generated properly, use a general purpose JSON generator (such as Stig Brautaset’s JSON Framewark or yajl-objc) rather than ad hoc conversion.

JSON Framework:

@interface Person(SBJson)
-(id)proxyForJson;
@end

@implementation Person(SBJson)
-(id)proxyForJson {
return [NSDictionary dictionaryWithObjectsAndKeys:
    name,@"name",
    [NSNumber numberWithInt:registered],@"registered",
     nil];
}
@end

...
    ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
    [request setPostValue:[[Person select] JSONRepresentation] forKey:@"json_key"];

yajl-objc:

@interface Person(YAJL)
-(id)JSON;
@end

@implementation Person(YAJL)
-(id)JSON {
return [NSDictionary dictionaryWithObjectsAndKeys:
    name,@"name",
    [NSNumber numberWithInt:registered],@"registered",
     nil];
}
@end

...
    ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
    [request setPostValue:[[Person select] yajl_JSONString] forKey:@"json_key"];

See also:

• Encoding custom classes using yajl-objc
• How to generate JSON programatically using JSON framework for iPhone
• Send NSMutableArray as JSON using JSON-Framework