The Core iOS Developer’s Cookbook, Fifth Edition

Recipe: Using JSON Serialization

The NSJSONSerialization class is tremendously handy when you’re working with JSON-based web services. All you need is a valid JSON container (namely an array or a dictionary) whose components are also valid JSON objects, including strings, numbers, arrays, dictionaries, and NSNull. Test an object’s validity with isValidJSONObject, which returns YES if the object can be safely converted to JSON format:

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// Build a basic JSON object NSArray *array = @[@"Val1", @"Val2", @"Val3"]; NSDictionary *dict = @{@"Key 1":array,     @"Key 2":array, @"Key 3":array}; // Convert it to JSON if ([NSJSONSerialization isValidJSONObject:dict]) {     NSData *data = [NSJSONSerialization         dataWithJSONObject:dict ...