Objective-C library to easily map NSDictionary to model objects, works perfectly with Alamofire. ObjectMapper works similar to GSON
Data Mapping library for Objective C
OCMapper is a data mapping library for Objective C that converts NSDictionary to NSObject. My inspiration behind writing OCMapper was to achieve two things:
- Simplify/Automate Data retrieval through web services
- Avoid adding parsing logic to model objects (I’m a big fan of separation of responsibilities!!!)
Swift Support
OCMapper takes advantage of the objective c runtime API, and will only work with classes that inherit from NSObject.
** Don’t use OCMApper with classes written in swift **
Alamofire Extension
https://github.com/Alamofire/Alamofire
public extension Request {
public func responseObjects<T: NSObject> (type: T.Type, completion: (NSURLRequest, NSURLResponse?, [T]?, NSError?)->()) -> Self {
return response(serializer: Request.JSONResponseSerializer(options: .AllowFragments)) { request, response, json, error in
if let error = error {
completion(request, response, nil, error)
}
else {
let objects = ObjectMapper.sharedInstance().objectFromSource(json, toInstanceOfClass: type) as? [T]
completion(request, response, objects, nil)
}
}
}
public func responseObject<T: NSObject> (type: T.Type, completion: (NSURLRequest, NSURLResponse?, T?, NSError?)->()) -> Self {
return response(serializer: Request.JSONResponseSerializer(options: .AllowFragments)) { request, response, json, error in
if let error = error {
completion(request, response, nil, error)
}
else {
let object = ObjectMapper.sharedInstance().objectFromSource(json, toInstanceOfClass: type) as? T
completion(request, response, object, nil)
}
}
}
}
Extension Usage
let request = Manager.sharedInstance.request(requestWithPath("example.com/users", method: .GET, parameters: nil))
request.responseObjects(User.self) { request, response, users, error in
// users is an array of User objects
}
let request = Manager.sharedInstance.request(requestWithPath("example.com/users/5", method: .GET, parameters: nil))
request.responseObject(User.self) { request, response, user, error in
// user is an instance of User
}
Features:
- Supports array mapping
- Supports tree structure mapping
- Auto maps everything based on key/values
- You can write mapping for non-matching dictionary/property keys
- Override portion of mapping using transformers
- Supports Core Data (NSManagedObjects mapping)
- Does not require subclassing or adding any extra code to your models
- Auto date conversion, and configurable DateFormatters
- Auto underscore to camel case mapping
Examples
@interface User
@property (nonatomic, strong) NSString *firstName;
@property (nonatomic, strong) NSString *lastName;
@property (nonatomic, strong) NSNumber *age;
@property (nonatomic, strong) NSDate *dateOfBirth;
@property (nonatomic, strong) NSDate *accountCreationDate;
@property (nonatomic, strong) Address *address;
@property (nonatomic, strong) NSMutableArray *posts;
@end
@interface Address
@property (nonatomic, strong) NSString *city;
@property (nonatomic, strong) NSString *country;
@end
@interface Post
@property (nonatomic, strong) NSString *title;
@property (nonatomic, strong) User *author;
@property (nonatomic, strong) NSDate *datePosted;
@end
Simple Automatic Mapping
{
"firstName" : "Aryan",
"lastName" : "Ghassemi",
"age" : 26,
"dateOfBirth" : "01/01/2013"
}
User *user = [User objectFromDictionary:aDictionary];
Nested Automatic Mapping
In this case everything is mapped automaticly because all key/values are similar.
“address” will automatically convert to “Address” Object.
“posts” will automatically convert to an array of “Post” objects.
The library detect the plural nouns, and finds the right class to be used for mapping
{
"firstName" : "Aryan",
"lastName" : "Ghassemi",
"age" : 26,
"dateOfBirth" : "01/01/2013",
"address" : {
"city" : "San Diego",
"country" : "US"
},
"posts" : [
{
"title" : "Post 1 title",
"datePosted : "04/15/2013",
},
{
"title" : "Post 2 title",
"datePosted : "04/12/2013",
}
]
}
User *user = [User objectFromDictionary:aDictionary];
Complex Mapping
Here is a more complex scenario where the dictionary keys do not match the model property names.
The key for date of birth changes from “dateOfBirth” to “dob”, and the key for “author” is named “from”
{
"firstName" : "Aryan",
"lastName" : "Ghassemi",
"age" : 26,
"dob" : "01/01/2013",
"address" : {
"city" : "San Diego",
"country" : "US"
},
"posts" : [
{
"title" : "Post 1 title",
"datePosted : "04/15/2013",
"from" : {
"firstName" : "Chuck",
"lastName" : "Norris"
}
},
{
"title" : "Post 2 title",
"datePosted : "04/12/2013",
"form" : {
"firstName" : "Chuck",
"lastName" : "Norris"
}
}
]
}
// Handle different key for dateOfBirth
[inCodeMappingProvider mapFromDictionaryKey:@"dob" toPropertyKey:@"dateOfBirth" forClass:[User class]];
// Handle mapping of "form" to "auther" object
// Mapping would NOT be required if dictionary key and property were both named the same
[inCodeMappingProvider mapFromDictionaryKey:@"from" toPropertyKey:@"author" withObjectType:[User class] forClass:[Comment class]];
User *user = [User objectFromDictionary:aDictionary];
Mapping Array on root level
[
{
"firstName" : "Aryan",
... rest of JSON data ...
},
{
"firstName" : "Chuck",
... rest of JSON data ...
},
]
NSArray *users = [User objectFromDictionary:aDictionary];
Flat Data to Complex Object
This is no longer enabled on default in order to improve performance. There is a property named normalizeDictionary in ObjectMapper class that allows you to turn this feature on if needed.
{
"firstName" : "Aryan",
"city" : "San Diego"
"country" : "United States"
}
// We map city and country to a nested object called 'address' inside the 'user' object
[self.mappingProvider mapFromDictionaryKey:@"city" toPropertyKey:@"address.city" forClass:[User class]];
[self.mappingProvider mapFromDictionaryKey:@"country" toPropertyKey:@"address.country" forClass:[User class]];
User *user = [User objectFromDictionary:aDictionary];
NSLog(@"FirstName:%@ City:%@ Country:%@",
user.firstName,
user.address.city,
user.address.coutnry);
Date Conversion
Automapper has a property named defaultDateFormatter, and when the property is set it’ll use this NSDateFormatter for date conversions on all NSDate properties. It’s recomended to set the defaultDateFormatter for best performance. Note that custom dateFormatters have priority over defaultDateFormatter
[inCodeMappingProvider setDefaultDateFormatter:aDefaultDateFormatter];
ObjectMapper uses a list of common NSDateFormatters to convert string to NSDate. Here is a list of common dateFormats supported out of the box
"yyyy-MM-dd"
"MM/dd/yyyy"
"yyyy-MM-dd'T'HH:mm:ss.SSSSSSSZ"
"yyyy-MM-dd HH:mm:ss"
"MM/dd/yyyy HH:mm:ss aaa"
"yyyy-MM-dd'T'HH:mm:ss'Z'"
You can also have custom NSDateFormatter specific to classes & properties
NOTE: Setting DateFormatter is not required as long as all date formats are standard or if the defaultDateFormatter knows how to parse the dates. The code below is just to demonstrate that it’s possible to set custom dateformatters but it is not required due to use of standard date formats in this example.
{
"firstName" : "Aryan",
"accountCreationDate" : "01/21/2005"
"dateOfBirth" : "2005-21-01"
}
// Custom formatter for account creation date
NSDateFormatter *accountCreationFormatter = [[NSDateFormatter alloc] init];
[accountCreationFormatter setDateFormat:@"MM/dd/yyyy"];
[inCodeMappingProvider setDateFormatter:accountCreationFormatter forProperty:@"accountCreationDate" andClass:[User class]];
// Custom formatter for date of birth
NSDateFormatter *dateOfBirthFormatter = [[NSDateFormatter alloc] init];
[dateOfBirthFormatter setDateFormat:@"yyyy-dd-MM"];
[inCodeMappingProvider setDateFormatter:dateOfBirthFormatter forProperty:@"dateOfBirth" andClass:[User class]];
User *user = [User objectFromDictionary:aDictionary];
Data Transformers
Data transformers allow you to capture a certain part of mapping and manually map it. It alsso opens room for polymorphic mapping.
Transform a field to another
{
"firstName" : "Aryan",
"country" : "United States"
}
@implementation User
@property(nonatomic, strong) NSString *firstName;
@property(nonatomic, strong) Country *country;
@end
[mappingProvider mapFromDictionaryKey:@"country" toPropertyKey:@"country" forClass:[User class] withTransformer:^id(id currentNode, id parentNode) {
return [[Country alloc] initWithName:currentNode];
}];
Using transformer for polymorphic relationships
{
"firstName" : "Aryan",
"vehicleType" : "car",
"vehicle" : { /*specific product Info*/ },
}
@implementation User
@property(nonatomic, strong) NSString *firstName;
@property(nonatomic, strong) Vehicle *vehicle;
@end
[mappingProvider mapFromDictionaryKey:@"vehicle" toPropertyKey:@"vehicle" forClass:[User class] withTransformer:^id(id currentNode, id parentNode) {
NSString *productType = [parentNode objectForKey:@"vehicleType"];
Vehicle *vehicle;
if ([productType isEqual:@"car"])
{
vehicle = [Car objectFromDictionary:currentNode];
}
else if ([productType isEqual:@"bike"])
{
vehicle = [Bike objectFromDictionary:currentNode];
}
return vehicle;
}];
// Or event better
[mappingProvider mapFromDictionaryKey:@"vehicle" toPropertyKey:@"vehicle" forClass:[User class] withTransformer:^id(id currentNode, id parentNode) {
NSString *productType = [parentNode objectForKey:@"vehicleType"];
Class class = NSClassFromString(productType.capitalizedString);
return [class objectFromDictionary:currentNode];
}];
Other posibilities with the transformer
{
"firstName" : "Aryan",
"image" : "BASE64_ENCODED_STRING"
}
@implementation User
@property(nonatomic, strong) NSString *firstName;
@property(nonatomic, strong) UIImage *image;
@end
[mappingProvider mapFromDictionaryKey:@"image" toPropertyKey:@"image" forClass:[User class] withTransformer:^id(id currentNode, id parentNode) {
return [UIImage imageFromBase64String:currentNode];
}];
Inverse mapping
Inverse mapping referrs to mapping of an object to a dictionary. This is very similar to a standard dictionary to property mapping. The following methods can be used in order to setup custom mapping for object to dictionary mapping.
- (void)mapFromPropertyKey:(NSString *)propertyKey toDictionaryKey:(NSString *)dictionaryKey forClass:(Class)class;
- (void)mapFromPropertyKey:(NSString *)propertyKey toDictionaryKey:(NSString *)dictionaryKey forClass:(Class)class withTransformer:(MappingTransformer)transformer;
- (void)setDateFormatter:(NSDateFormatter *)dateFormatter forDictionary:(NSString *)property andClass:(Class)class;
InCodeMappingProvider class has a property named automaticallyGenerateInverseMapping. This property is set to true on default, which means whenever a dictionary-to-property mapping is set, an inverse-mapping is automatically generated, and therefore there is no need to manually write mapping for object-to-dictionary mapping. The only exception is that mapping dictionary-to-property with data-transformers cannot be automatically inversed.
Date formatters are also created for an inverse relationship when automaticallyGenerateInverseMapping is set to true.
Core Data Support
In order to use core data you can add a ManagedObjectInstanceProvider to ObjectMapper
ManagedObjectInstanceProvider *instanceProvider = [[ManagedObjectInstanceProvider alloc] initWithManagedObjectContext:moc];
[[ObjectMapper sharedInstance] addInstanceProvider:instanceProvider];
On default Object mapper creates a new instance of NSManagedObject on every mapping. In order to update an existing record you could provide unique keys for a given class and ObjectMapper would automatically update the existing record.
[managedObjectInstanceProvider setUniqueKeys:@[@"userId"] forClass:[User class] withUpsertMode:UpsertModePurgeExistingObject];
When assigning keys for classes OCMApper also requires an enum describes how ObjectMapper should upsert existing records.
-
UpsertModeUpdateExistingObject: This option creates a new temporary instance of managed object, and then based on the given keys it attempts to find an existing record. If it finds ONE record it updates all properties of the existing managed object and finally removes the temporary object. When using this upsert mode, delete does not get called on any of the related managed objects, and therefore records remain in memory. For instance if the user’s address has changed from A to B address would be updated properly, but both records would remain in core data.
-
UpsertModePurgeExistingObject: This option creates a new instance of managed object, and then based on the given keys it attempts to find an existing record. If it finds ONE record it calls delete on that record, and then inserts the newly created object into context. Using this upser mode, delete gets called on existing managed object, and therefore core data would delete all related relational objects, and all “delete rules” in core data model would be applied. For instance, if a user get’s updated, and phone number changes from A to B, and if trhe delete rule is marked as cascade, then Address A would be removed and address B would be assigned to the user.
Different Usage & Helpers
// Using ObjectMapper Directly
ObjectMapper *mapper = [[ObjectMapper alloc] init];
Urse *user = [mapper objectFromSource:dictionary toInstanceOfClass:[User class]];
// Using ObjectMapper Singleton Instance
Urse *user = [[ObjectMapper sharedInstance] objectFromSource:dictionary toInstanceOfClass:[User class]];
In order to use these categories you must add your mapping provider to the singleton Instance
// Using NSObject Category
User *user = [User objectFromDictionary:aDictionary];
// Using NSDictionary Category
User *user = [aDictionary objectForClass:[User class]];
Change Log
2.1
Allow automatic conversion of underscore keys to camelCase properties
first_nametofirstNameasStringemail_confirmationtoemailConfirmationasEmailConfirmationclassemail_confirmationstoemailConfirmationsasNSArray of EmailConfirmationclass
2.0
Fixed a bug that was instroduced in 1.8 where classes with two words in they weren’t getting mapped automatically.
EX (sessionUser would try to map to Sessionuser class instead of SessionUser and would fail to map)
1.9
Automatic NSString to NSNumber and NSNumber to NSString conversion
1.8
- No longer loading bundle class names in memory on init
- Fixed for #22
- No longer need to write mapping for non-array pointers as long as key/property names match (ex: “location” key would automatically map to “location” property event if the class type is named “Address” )
- Wrote tests for mapping swift classes
Note:
Automatic mapping treats nested array differently. ObjectMapper capitalizes the first character of the dictionary key before checking for a conversion class.
- “UserAddress” will automatically be mapped to “UserAddress”
- “userAddress” will automatically be mapped to “UserAddress”
- “useraddress” will NOT be mapped to “UserAddress”, you need to manually write mapping