Setting property values programmatically in objective c

Question

I have a file Variables.m for storing properties that I can use in all classes within my app. Now I would like to set a value for one of the properties (say username) in class A and I would like it to be available to all the other classes (B,C,D,E..) in my app like a constant. ie. once they initialize a Variables object (say var) in class B, if they issue var.username, they should get the username that I set in class A.

In effect instead of hardcoding a username value, I want to set it programmatically and have all the classes see the value that I just set. Can I achieve this without passing the Variables object around whenever I navigate to a class?

Inder Kumar Rathore · Accepted Answer · 2012-08-31 15:00:16Z

2

Alternatively, you can use NSUserDefaults

Set variable in class A:

NSString *usernameToSave = @"John Doe";
[[NSUserDefaults standardUserDefaults] setObject:usernameToSave forKey:@"userName"];

Read variable in any class:

NSString *userName = [[NSUserDefaults standardUserDefaults] objectforKey:@"userName"];

Apart from being simple, this has the advantage (or not) that it's persistent across app restarts.

It has the disadvantage that it's not very secure; for passwords and the like you should use Keychain Services as described here.

edited Aug 31, 2012 at 15:00

Inder Kumar Rathore

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answered Aug 31, 2012 at 14:25

Wildaker

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Comments

AppHandwerker · Accepted Answer · 2012-08-31 14:22:26Z

1

Create a singelton class that has the appropriate getters and setters for the items you want it to store.

You can then just reference that single instance from any other class.

For example in your Variables class create a class method like so:

    +(Variables*)sharedVariables{
        static Variables *myVariables = nil;
        if (myVariables != nil){
             return myVariables;
        }
       myVariables = [[Variables alloc]init];
       return myVariables;
    }

If you want a better implementation then google objective C singleton class implementation.

:)

to use this from your other classed you would just type:

[Variables sharedVariables].whatever

edited Aug 31, 2012 at 14:22

answered Aug 31, 2012 at 14:17

AppHandwerker

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3 Comments

vivek Over a year ago

Thanks but I have a couple of question. In your singleton class if I wanted to initialize it with values, say username and password, how do I do this. Also can I have 2 versions of sharedVariables, one that takes in input arguments and allocates the space for the static myVariables object and the other that just returns the myVariables object? If yes where do I put the statement static Variables *myVariables = nil ? Thanks

AppHandwerker Over a year ago

set those in the init method. Or create a custome one i.e. -(id)initWithMyData:(Type*)data1 andData2:(Type*)data2; if they are going to change otherwise just type them in the standard initialiser for that class.

AppHandwerker Over a year ago

well this a singleton. So there should only be one. If you want a singe instance that you can reference from other classes use the class method above to create a singleton. if you want another instance if this class then just use the standard init method to create those.

Padavan · Accepted Answer · 2012-08-31 14:18:37Z

0

You can use Singleton pattern. Like this.

@interface MySingleton : NSObject 
{
    NSString *username;
}
@property (nonatomic, retain) NSString *username;
+ (MySingleton *) sharedInstance;

@end


@implementation MySingleton
@synthesyse username;
static MySingleton *sMySingleton = nil;

+ (MySingleton *) sharedInstance
{
    @synchronized(self)
    {
        if (sMySingleton == nil)
        {
            sMySingleton = [NSAllocateObject([self class], 0, NULL) init];
        }
    }    
    return sMySingleton;
}

@end

answered Aug 31, 2012 at 14:18

Padavan

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