Question

I have the following issue. I have two classes that manipulate information but they are completely disconnected, i.e. I can’t reach the other class.

I need both classes to use a certain value. For example, class A sets the value foo = A and class B needs to be able to read that value and rest foo to nil.

I thought about creating the variable in the main app delegate, but can’t figure out how.

Ideas?!!

Answer 1

Global variables are generally bad idea. Based on your description i think you can use KVO to inform class B about the changes in ‘foo’.

But if you relly need a global variable you can do this:

@interface YourAppDelegate : NSObject <UIApplicationDelegate> {
}
@property (nonatomic) NSString *foo;
@end

@implementation YourAppDelegate
@synthesize foo;
...
@end


@implementation ClassA
...
- (void)someMethod {
YourAppDelegate *appDelegate = (YourAppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.foo = @"NewValueOfFoo";
}
...
@end


@implementation ClassB
...
- (void)otherMethod {
YourAppDelegate *appDelegate = (YourAppDelegate *)[[UIApplication sharedApplication] delegate];
NSLog(@"Value of foo: %@", appDelegate.foo);  //This will print: "Value of foo: NewValueOfFoo"
}
...
@end