Basic MVC: set variable to NSTextField input in different classes - objective-c

Question

The main idea:
Model: Set the value from the textfield to a variable which I can call/log.
View: Just a NSTextField hooked up to the Model class.
Controller: NSButton hooked up to the ViewController.
As you will notice, it logs the basic string from NSLog, also the predefined beginvalue. but when I ask for the txtBegin value it returns NULL
I know the TextField and the Button are hooked up in the connections inspector.
Screenshot:
Downloadable project:
ViewController.h
#import <Cocoa/Cocoa.h>
#import "Model.h"
#interface ViewController : NSView
- (IBAction)logTheVariable:(id)sender;
#end
ViewController.m
- (IBAction)logTheVariable:(id)sender
{
Model *myModel = [[Model alloc]init];
[myModel doSomething];
}
Model.h
#import <Foundation/Foundation.h>
#interface Model : NSObject{
//iVars
int begin;
}
//properties
#property (weak) IBOutlet NSTextField *txtBegin;
//methods
-(void)doSomething;
#end
Model.m
#import "Model.h"
#implementation Model
-(void)doSomething{
NSLog(#"I'm in the Model Class"); //logs like a charm!
begin = 5; //just a test to see if it logs anything (which works)
NSLog(#"%d",begin);// logs like a charm!
//->Problem is here <-
NSLog(#"%#",_txtBegin.stringValue); //returns a "NULL" value.
//->Problem is here <-
}
#end

Answer 1

Simple solution just declare the outlet of textfield in your viewcontroller and then modify below method in your model class and implement it:-
Model.h
-(void)doSomething: (NSString*)yourstringvalue;
Model.m
-(void)doSomething: (NSString*)yourstringvalue
{
NSLog(#"%#",yourstringvalue);
}
Viecontroller.m
- (IBAction)logTheVariable:(id)sender
{
Model *myModel = [[Model alloc]init];
NSString * str=self.begintext.stringValue;
[myModel doSomething:str];
}

Answer 2

The Model class instance you use in logTheVariable: is logging a null value because it is a new instance you created in the action of the ViewController, not an instance of Model interface builder is aware of.
- (IBAction)logTheVariable:(id)sender
{
Model *myModel = [[Model alloc]init];
//This is a new instance. The IBOutlet for txtBegin is null.
[myModel doSomething];
}
What you have implemented is not how MVC is intended. Apple provides a thorough roadmap of the user interface, framework and programming concepts you need to know to develop for OSX that will help you understand how Apple expects you to use their frameworks. https://developer.apple.com/library/mac/referencelibrary/GettingStarted/RoadMapOSX/chapters/01_Introduction.html
Models generally don't know anything about the user interface. They just store data and communicate when data is changed.
Your Model class should expose a property for any data it wants to expose.
Your Model class should not have any reference to the NSTextField.
So now in your model, you can log when your property is changed
-(void)doSomething:(NSString *)value //method name should be setBegin assuming you name your property 'begin'
{
NSLog(#"I'm in the Model Class"); //logs like a charm!
begin = 5; //just a test to see if it logs anything (which works)
NSLog(#"%d",begin);// logs like a charm!
//->Problem is here <-
NSLog(#"%#",value); //will log like a charm
}
Views generally doesn't know anything about the model. It just displays data in a way the user can interact with and possibly edit.
Controllers tie the Model and View together. It receives notification from the model when data changes and updates the View. Conversely, it also receives notification from the View when the data is edited to update the Model.
Your ViewController class should have a reference to the NSTextField (using an outlet)
Your ViewController class should have an instance of Model which it creates internally.
Now your logTheVariable can be implemented to tie the Model and View together:
- (IBAction)logTheVariable:(id)sender
{
//Use ViewController's model instance
Model *myModel = [self myModel];
NSString * value = [[self txtBegin] stringValue];
[myModel doSomething:value];
}