JSON Tools (Objective-C)

by Gregory Combs
(MIT License - 2014)

JSON Patch, JSON Pointer, and JSON Schema Validation in Objective-C

This Objective-C library is a collection of classes and categories that implement three powerful new features (JSON Patch, JSON Pointer, JSON Schema) that work with JSON data (represented by NSDictionaries and NSArrays in Objective-C). Unit tests are included for each component.

To Run the Tests

To build the test project, be sure to do the following:

1. Install CocoaPods (use homebrew) if you haven't already.
2. Run pod install from the command line.
3. Open the newly created JSONToolsTests.xcworkspace document not the JSONToolsTests.xcodeproj document.
4. Hit Command-U to run the tests.

Features

• JSON Patch - IETF RFC6902: Create and apply operation patches (add, remove, copy, move, test, _get) to serially transform JSON Data. This functionality was inspired by Joachim Wester'sJavaScript implementation of JSON Patch.

  • Example Patch Copy:

     #import"JSONTools.h"
    #import"JSONDeeplyMutable.h"
    - (void)examplePatchCopy
    {
    NSMutableDictionary *obj = nil;
    NSMutableDictionary *expected = nil;
    NSDictionary *patch = nil;
    obj = [@{@"foo": @1,
    @"baz": @[@{@"qux": @"hello"}]} copyAsDeeplyMutableJSON];
    patch = @{@"op": @"copy",
    @"from": @"/foo",
    @"path": @"/bar"};
    [JSONPatch applyPatches:@[patch] toCollection:obj];
    expected = [@{@"foo": @1,
    @"baz": @[@{@"qux": @"hello"}],
    @"bar": @1} copyAsDeeplyMutableJSON];
    }
    

  • Example Patch Generation (JSON Diff):

     #import"JSONTools.h"
    - (void)examplePatchGeneration
    {
    NSDictionary *objA = nil;
    NSDictionary *objB = nil;
    NSArray *patches = nil;
    NSArray *expected = nil;
    objA = @{@"user": @{@"firstName": @"Albert",
    @"lastName": @"Einstein"}};
    objB = @{@"user": @{@"firstName": @"Albert"}};
    patches = [JSONPatch createPatchesComparingCollectionsOld:objA toNew:objB];
    expected = @[@{@"op": @"remove",
    @"path": @"/user/lastName"}];
    }
    

• JSON Pointer - IETF RFC6901: Reference and access values and objects within a hierarchical JSON structure using a concise path pattern notation. This functionality is based on Jonathan Dring'sNSDictionary-CWJSONPointer.

  • Example:

     #import"JSONTools.h"
    - (void)exampleJSONPointer
    {
    NSDictionary *obj = @{
    @"data": @{
    @"foo": @[@"bar", @"baz"],
    @"bork": @{
    @"crud": @"stuff",
    @"guts": @"and things"
    }
    }
    };
    NSString *result1 = [_obj valueForJSONPointer:@"/data/foo/1" ];
    // Yields -> "baz"NSString *result2 = [_obj valueForJSONPointer:@"/data/bork/guts"];
    // Yields -> "and things"NSDictionary *result3 = [_obj valueForJSONPointer:@"/data/bork"];
    // Yields -> {"crud": "stuff","guts": "and things"}
    }
    

• JSON Schema with Validation - IETF Draft v4, 2013. This functionality is based on Sam Duke'sKiteJSONValidator but adds additional validations and tests for the JSON-Schema format parameter.

  • Example #1:

     {
    "schema": {
    "type": "array",
    "items": { "$ref": "#/definitions/positiveInteger" },
    "definitions": {
    "positiveInteger": {
    "type": "integer",
    "minimum": 0,
    "exclusiveMinimum": true
    }
    }
    },
    "validData": [0, 1, 2, 3, 4, 5],
    "invalidData": [-12, "Abysmal", null, -141]
    }

    /* Assuming that variables are assigned using JSON above:  schema is an NSDictionary validData and invalidData are NSArrays*/BOOL success = NO; JSONSchemaValidator *validator = [JSONSchemaValidator new];
    success = [validator validateJSONInstance:validData withSchema:schema];
    // success == YES, All validData values are positive integers.
    success = [validator validateJSONInstance:invalidData withSchema:schema];
    // success == NO, invalidData array isn't comprised of positive integers.

  • Example #2:

    NSDictionary *schema = nil;
    id testData = nil;
    BOOL success = NO;
    JSONSchemaValidator *validator = [JSONSchemaValidator new];
    validator.formatValidationEnabled = YES;
    schema = @{@"format": @"date-time"};
    testData = @"2000-02-29T08:30:06.283185Z";
    success = [validator validateJSONInstance:testData withSchema:schema];
    // success == YES, February 2000 had 29 days.
    schema = @{@"format": @"ipv6"};
    testData = @"12345::";
    success = [validator validateJSONInstance:testData withSchema:schema];
    // success == NO, the IPv6 address has out-of-range values.