CODEWITHSUNDEEP
iphoneiosnsmutabledictionarynsobject
Khushbu Shah
Khushbu Shah

Reputation: 1683

how to store custom objects in NSMutableDictionary?

I'm new to iOS. I have a class derived from NSObject and I want to store its reference into NSMutableDictionary. How can I? e.g.

    @interface CustomClass : NSObject
    {
    }

I want to store reference (*customClass) of this CustomClass into NSMutableDictionary. Please give me the simple way to store and retrieve it.

Upvotes: 2

Views: 5102

Answers (6)

Nitesh Borad
Nitesh Borad

Reputation: 4663

For that purpose, you need to use NSKeyedArchiver and NSCoder classes, as following:

In your CustomClass.m file, implement the following two encoding and decoding methods :

- (void)encodeWithCoder:(NSCoder *)encoder {
    // encoding properties 
    [encoder encodeObject:self.property1 forKey:@"property1"];
    [encoder encodeObject:self.property2 forKey:@"property2"];
}

- (id)initWithCoder:(NSCoder *)decoder {
    if((self = [super init])) {
        // decoding properties 
        self.property1 = [decoder decodeObjectForKey:@"property1"];
        self.property2 = [decoder decodeObjectForKey:@"property2"];
    }
    return self;
}

Use it for setting and getting object like this:

 // For setting custom class objects on dictionary

 CustomClass * object = /*..initialisation....*/;
 NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:object];
 [dictionary setObject:encodedObject forKey:key];

 // For getting custom class objects from dictionary

 NSData *encodedObject = [dictionary objectForKey:key];
 CustomClass * object = (CustomClass *)[NSKeyedUnarchiver unarchiveObjectWithData:encodedObject];

UPDATE: Better way is to use simple and easy to use third party library: RMMapper - https://github.com/roomorama/RMMapper

Upvotes: 4

Ander
Ander

Reputation: 3698

When storing an object in a NSMutableDictionary you are storing a reference (pointer) to the object, not the object itself. So you don't need to treat objects of your CustomClass any differently to standard objects.

All the following will work:

    CustomClass *customObject;

    NSMutableDictionary *mutableDictionary = [[NSMutableDictionary alloc] initWithObjectsAndKeys:customObject, @"key", nil];
    [mutableDictionary setObject:customObject forKey:@"key"];
    CustomClass *retrievedObject = [mutableDictionary objectForKey:@"key"];

Upvotes: 0

Ben Boral
Ben Boral

Reputation: 355

Let's say you want to create a NSMutableDictionary iVar in a UIViewController class called ViewController.

ViewController.h:

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController{
}
@property (nonatomic, strong) NSMutableDictionary *mutDict;

@end

ViewController.m

#import "ViewController.h"
#import "CustomClass.h"

@interface ViewController ()
@end

@implementation ViewController
@synthesize mutDict=_mutDict;

-(void)viewDidLoad{
 [super viewDidLoad];
 CustomClass *cc1=[[CustomClass alloc] init];
 CustomClass *cc2=[[CustomClass alloc] init];
 self.mutDict=[[NSMutableDictionary alloc] initWithObjectsAndKeys: cc1, @"key1", cc2, @"key2", nil];
}

@end

Please note that I did not do any memory management in this example (assuming ARC), and I have not tested this code.

Upvotes: 0

rano
rano

Reputation: 5666

A NSMutableDictionary is a NSDictionary in which you can dynamically add and remove pairs in the for of value-key.

You simply have to specify some key value to pair it when you add a custom object in it (ie a NSString).

 CustomClass * myObj = ... //declared and initialized obj

 NSMutableDictionary * myDict = [[NSMutableDictionary alloc] init]; //declared and initialized mutable dictionary

 [myDict setObject:myObj forKey:@"first"]; //assigning a string key to the object

 NSLog(@"My first object was %@", [myDict objectForKey:@"first"]); //retrieving the object using its key. It will print its reference

 CustomClass * anotherObj = (CustomClass *)[myDict objectForKey:@"first"]; //retrieving it and assigning to another reference obj. It returns a NSObject, you have to cast it

 [myDict removeObjectForKey:@"first"]; //removing the pair obj-key
 NSLog(@"My first object was %@", [myDict objectForKey:@"first"]); //cannot find it anymore

Here is a little tutorial with NSDictionaries.

Upvotes: 0

Sanoj Kashyap
Sanoj Kashyap

Reputation: 5060

Use 

 NSMutableDictionary *obect = [[NSMutableDictionary alloc] initWithObjects:CustomObject forKeys:@"Customobjectkey"];

you can get the object with this key "Customobjectkey" and type cast that object as per the class.

Upvotes: 0

janusfidel
janusfidel

Reputation: 8106

//store
NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithObject:customClass forKey:@"myCustomClass"];

//retrieve
CustomClass *c = (CustomClass*)[dictionary objectForKey:@"myCustomClass"]

Upvotes: -1

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