Objective-C

Get the Index of a JSON Member

See more JSON Examples

This example demonstrates how to get the index of a given member by name.

{
  "name": "donut",
  "image":
    {
    "fname": "donut.jpg",
    "w": 200,
    "h": 200
    },
  "thumbnail":
    {
    "fname": "donutThumb.jpg",
    "w": 32,
    "h": 32
    }
}

Objective-C

#import <CkoJsonObject.h>
#import <NSString.h>

BOOL success = NO;

CkoJsonObject *json = [[CkoJsonObject alloc] init];

// This is the above JSON with whitespace chars removed (SPACE, TAB, CR, and LF chars).
// The presence of whitespace chars for pretty-printing makes no difference to the Load
// method. 
NSString *jsonStr = @"{\"name\": \"donut\",\"image\":{\"fname\": \"donut.jpg\",\"w\": 200,\"h\": 200},\"thumbnail\":{\"fname\": \"donutThumb.jpg\",\"w\": 32,\"h\": 32}}";

success = [json Load: jsonStr];
if (success == NO) {
    NSLog(@"%@",json.LastErrorText);
    return;
}

// The top-level JSON object has three members: name, image, and thumbnail.
int nameIndex = [[json IndexOf: @"name"] intValue];
// The index of the "name" member is 0.
NSLog(@"%@%d",@"nameIndex = ",nameIndex);

int thumbIndex = [[json IndexOf: @"thumbnail"] intValue];
// The index of the "thumbnail" member is 2.
NSLog(@"%@%d",@"thumbIndex = ",thumbIndex);

// The "fname" member is NOT a direct member of the top-level JSON object.
// It is a member of a nested object.  If we try to get the index of this
// member using the top-level JSON object, it is not found (and returns -1).
int fnameIndex = [[json IndexOf: @"fname"] intValue];
// The fnameIndex is -1 (not found).  This is correct.
NSLog(@"%@%d",@"fnameIndex = ",fnameIndex);

// Get the "image" object.
CkoJsonObject *imageObj = [[CkoJsonObject alloc] init];
[json ObjectOf2: @"image" jsonObj: imageObj];

// Now we can get the index of the "fname" object, because it is a direct
// member of the "image" object:
fnameIndex = [[imageObj IndexOf: @"fname"] intValue];
NSLog(@"%@%d",@"fnameIndex = ",fnameIndex);