communicating between classes with pointers - objective-c

Question

Hi all,
I'm having a hard time understanding how to use pointers
(my first time using them) hoping someone can point me in the right
direction (no pun intended) :P
(it controls the sound,pagenumber,bg,audio int, and text to be displayed)
(NSString *)textFromPlist pointer which points to the plist containing the text for #"Page01Text"
I want to take #"Page01Text" and use it in the HighLighter class
I am able to log the output for the sound,pagenumber,bg,audio int, and text etc in the hello world layer (its logging the TextManagerWithpageNum) so I know that the plist is reading,
but for some reason I cant link textFromPlist I'd like to be able to use the textFromPlist from the TextManagerWithpageNum class and let the hilighter class work with it (this class will hilight the text and work with the audio intervals supplied by the plist)
this piece of code it returns (NULL)
#interface HighLighter.h
TextManagerWithpageNum *myClassAccess;
//declaring the TextManagerWithpageNum class so I can access textFromPlist
#implementation HighLighter.m
-(NSString *)Sentance01
{
NSString *textFromTextManager = myClassAccess.textFromPlist;
NSString *storyText = [NSString stringWithFormat:#"%#",textFromTextManager];
return [[[NSString alloc]initWithString:StoryText]autorelease];
//doesn't crash but doesn't load text
NSLog(#"text form plist #%",storyText);
}
What is it that I am doing wrong? (I have an int array I also wish to link, but thought I'd start with the NSString as I thought this would be simpler.)
any help would be wonderful, kind regards,
Natalie.
#interface TextManagerWithpageNum : CCLayer
NSString* textFromPlist_Pntr;
#property(nonatomic, readonly) NSString* textFromPlist;
//NSString* textFromPlist is an item on the plist #"page01" which contains text for the page
#property(nonatomic, readonly) NSString* audioInterval;
//NSString* AudioInterval is an array on the plist #"AudioTimings_PG01"
#implementation TextManagerWithpageNum
#synthesize textFromPlist = textFromPlist_Pntr;
#synthesize audioInterval = _audioInterval;

Answer 1

There are a couple of options when communicating any data between classes. I will show both, using an example SomeData object that is being sent from ObjectA to ObjectB. You can also use class level methods to, for example, send or receive data in a pointer to a singleton object. I won't show you how to do that because it doesn't sound like that fits your problem.
Option 1
Define a receiving message in ObjectB.
#interface ObjectA
{
SomeData *someDataPointer;
ObjectB *someObjectB;
}
#end
#implementation ObjectA
-(void)someMethod
{
someDataPointer = [[SomeData alloc] init]; // Or whatever way you want to create and set someDataPointer
[someObjectB receiveData:someDataPointer];
// Note: if you will be calling receiveData on someObjectB much later than the
// time of creation of someDataPointer, you should retain someDataPointer to
// hold onto it until you need to pass it on.
// ie)
// [someDataPointer retain];
}
#end
#interface ObjectB
-(void)receiveData:(SomeData *)dataPtr;
#end
#implementation ObjectB
-(void)receiveData(SomeData *)dataPtr
{
// Here the data from someDataPointer will also be pointed to by dataPtr
// Use dataPtr now
[self doSomethingWithData:dataPtr];
}
#end
Option 2
Define a sending message in ObjectA.
#interface ObjectA
{
SomeData *someDataPointer;
}
#property (nonatomic, retain) SomeData *someDataPointer;
#end
#implementation ObjectA
#synthesize someDataPointer = someDataPointer_;
#end
#interface ObjectB
{
ObjectA *someObjectA;
}
#end
#implementation ObjectB
-(void)someMethod
{
SomeData *dataPtr = [someObjectA getSomeDataPointer];
// Now do something with dataPtr
}
#end
I hope that helps. I wanted to show you these two techniques generally so that you can learn to apply it to your case specifically. Let me know if you have questions.