How to create a "Typical methods" class?

[AdamsApple]

I am not sure what it is called, but I'd like to create a .m and .h with a few common functions so that i can call them from all of my viewcontrollers.
I have about 5 view controllers.

So here is what i did, which seems not to work.

I create a class and put the function in there:

in the CommonMethods.h

#import <Foundation/Foundation.h>

@interface CommonMethods : NSObject


-(UIImage*)processImage:(UIImage*)theImage;

@end

In the CommonMethods.m

#import "CommonMethods.h"

@implementation CommonMethods




-(UIImage*)processImage:(UIImage*)theImage {
	
// do things here (secret! :P)	
	
	//RETURN
	return theImage;
	
	
	
}


@end

So in my viewController, i add the import h part in the viewcontroller.m

#import "CommonMethods.h"

then to call, i just use

tmp = [self processImage:myImg];

But got a SIGABRT error.. obviously my vc does not recognize this function..

Please help what is the correct way to do this? Thank you.....

[fiftysixty]

Originally Posted by AdamsApple

I am not sure what it is called, but I'd like to create a .m and .h with a few common functions so that i can call them from all of my viewcontrollers.
I have about 5 view controllers.

So here is what i did, which seems not to work.

I create a class and put the function in there:

in the CommonMethods.h

#import <Foundation/Foundation.h>

@interface CommonMethods : NSObject


-(UIImage*)processImage:(UIImage*)theImage;

@end

In the CommonMethods.m

#import "CommonMethods.h"

@implementation CommonMethods




-(UIImage*)processImage:(UIImage*)theImage {
	
// do things here (secret! :P)	
	
	//RETURN
	return theImage;
	
	
	
}


@end

So in my viewController, i add the import h part in the viewcontroller.m

#import "CommonMethods.h"

then to call, i just use

tmp = [self processImage:myImg];

But got a SIGABRT error.. obviously my vc does not recognize this function..

Please help what is the correct way to do this? Thank you.....

There are a few ways to go about this. You could either create a class that has only so called class methods, or you could implement a singleton-pattern for your class. It seems you have a lot to learn, so I suggest you do some searching on objective-c class methods and the singleton design pattern before continuing. And obviously it would be a good idea to read some Apple documentation as well.

Get familiar with the basic concepts of object oriented programming, objective-c and some of the most basic design patterns (model-view-controller, singleton etc.) and then continue.

[bellissimo]

For general utility methods, I often just create a separate .h/.m file, but use standard C functions, rather that Objective-C.

Obviously though it depends on what you are doing. If you are creating some String manipulation functions for example, then it may well make more sense to create a Category on the NSString class instead, especially if you want them to act on a particular instance of an NSString.

[AdamsApple]

Hm... If anyone else can show me an exmple of how to do this would be great. I know i have a lot to learn bcause i am new in xcode, that's why i ask the question here. If i know, i wouldn't ask this question.....

Any other pepeol that can help me i will be extremely thankful.

[Music Man]

Originally Posted by AdamsApple

So in my viewController, i add the import h part in the viewcontroller.m

#import "CommonMethods.h"

then to call, i just use

tmp = [self processImage:myImg];

But got a SIGABRT error.. obviously my vc does not recognize this function..

Please help what is the correct way to do this? Thank you.....

Why are you calling [self processImage:myImg] ?

By calling self, you are referring to the viewController class, not the CommonMethods class.

The image method is in the CommonMethods class so you need to refer to that class:

Create an instance variable to your common methods class and use that.

#import <UIKit/UIKit.h>

@class CommonMethods;

@interface ViewController : UIViewController
{
    CommonMethods *commonMethods;
}



@end

Then import CommonMethods.h to your main viewController file - then implement this (in whatever method you want, I used viewDidLoad as an example).

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    UIImage *img = [UIImage imageNamed:@"test.jpg"];
    [commonMethods processImage:img];
}

or modify it to what you need.

Also what is tmp referring to in your example?

[AdamsApple]

Music Man, THANK YOU FOR YOUR ANSWER!
You are THE (music) MAN!


tmp is a UIImage.

Ok new problem, if you'd like to continue helping....

the method is recognized but it is not returning the UIImage
result. As I checked, it only returns 0x0. This is how I did it.

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    UIImage *img = [UIImage imageNamed:@"mytest.png"];
    
    myImage.image = [commonMethods processImage:img];
}

myImage.image contains 0x0 bytes after it. The processImage
is AOK, because when it is in the same viewcontroller, it works
fine.

Please help.... anyone.. tq....

[AdamsApple]

Ok I got it to work.

Here's the code:


Use a + sign for method instead of -
.h

#import <Foundation/Foundation.h>

@interface CommonMethods : NSObject


+(UIImage*)processImage:(UIImage*)theImage;

@end

.m

#import "CommonMethods.h"

@implementation CommonMethods




+(UIImage*)processImage:(UIImage*)theImage {
	
// do things here (secret! :P)	
	
	//RETURN
	return theImage;
	
	
	
}


@end

TO USE:

import the .h in your vc .m,

then directly call it

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    UIImage *img = [UIImage imageNamed:@"mytest.png"];
    
    myImage.image = [CommonMethods processImage:img];
}

there is no need to declare it as a class in the header of your vc as well.
I like this way, it is so simple.

Anyway, thanks again to Music Man for making it clear to me regarding
the "self" usage and what it actually means.