Question

I have use a singleton class that contained just one passed value. I then tried to add another one.

#import <Foundation/Foundation.h>

@interface GlobalValueContainer : NSObject {


    NSString *passedText;
    NSString *myPassedPictureName;
}


@property (nonatomic, strong) NSString* passedText;
@property (nonatomic, strong) NSString* myPassedPictureName;


+ (GlobalValueContainer *) sharedStore;

@end


#import "GlobalValueContainer.h"

@implementation GlobalValueContainer;

@synthesize passedText;
@synthesize myPassedPictureName;

static GlobalValueContainer *sharedStore = nil;


+ (GlobalValueContainer *) sharedStore {
    @synchronized(self){
        if (sharedStore == nil){
            sharedStore = [[self alloc] init];
        }
    }

    return sharedStore;
}


@end

From the first view I then try to set the myPassedPictureName

-(IBAction)setPicture:(id)sender{

    myPicture = @"Hus";
    GlobalValueContainer* localContainer = [GlobalValueContainer sharedStore];
    localContainer.myPassedPictureName = myPicture;


}

and on the second view I want to set an imageview with that name (+png that is)

- (void)viewDidLoad
{
    [super viewDidLoad];
    //Store* myStore = [Store sharedStore];


    GlobalValueContainer* localContainer = [GlobalValueContainer sharedStore];
    myPassedPictureName = localContainer.myPassedPictureName;
    myPicture.image = [UIImage imageNamed:myPassedPictureName];
    whatFile.text = myPassedPictureName;

   //object.imageView.image = [UIImage imageNamed:@"downloadedimage.png"];

}

the picture doesnt show. I have also tried to add a UIlabel and set the string that should have been passed. But it also turns out blank.

When I pass text using the “passedText” it works fine. When I added the second NSString, nothing happens?.

First things first. Can anyone see what´s wrong (still learning obj c here 🙂 and, is it the correct way I try to manipulate an UIImageView. I want to use the myPassedPictureName to set a picture on a number of UIViews depending on the button being pressed.

Looking forward to your input.

Answer 1

I’m quite sure using singleton for passing value like this is not a good idea.Singleton is not designed for passing value,but for doing something.So you can not use Property like

sharedManager.passValue
Here has some good discussion about singleton.
When should you use the singleton pattern instead of a static class?
and
What should my Objective-C singleton look like?

So I suggest write it like this:

#import <Foundation/Foundation.h>

@interface GlobalValueContainer : NSObject {

}

+ (id) sharedManager;
-(NSString*)myText;
-(NSString*)myPictureName;

@end


#import "GlobalValueContainer.h"

@implementation GlobalValueContainer;


static GlobalValueContainer *sharedManager = nil;


+ (id) sharedManager {
    @synchronized(self){
        if (sharedManager == nil){
            sharedManager = [[self alloc] init];
        }
    }

    return sharedManager;
}

-(NSString*)myText
{
    return @"your text";
}
-(NSString*)myPictureName
{ 
    return @"yourPictureName.png";
}  
@end