Disable Button Loop (NStimer or MouseMove) XCode Objective-C MacOS - objective-c

Question

I am just experimenting with disabling a button with various methods on XCode MacOS (not iOS) Cocoa Objective-C.
In this scenario I have a help button (m_btHelp) that is disabled when g_bEnableHelpButton = NO; but it is only being checked when the mouse moves.
-(void)mouseMoved:(NSEvent *)theEvent
{
if(g_bEnableHelpButton) {
[m_btHelp setEnabled:YES];
} else {
[m_btHelp setEnabled:NO];
}
I would rather have this continuously checked instead of only checked when the mouse moves. I have tried NSTimer with something like this, but it does not seem to work (m_btHelp does not get disabled when g_bEnableHelpButton = NO; like it does in the mouseMoved event:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(Timerloop) userInfo:nil repeats:YES];
}
- (void)Timerloop
{
if(g_bEnableHelpButton) {
[m_btHelp setEnabled:YES];
} else {
[m_btHelp setEnabled:NO];
}
}

Answer 1

g_bEnableHelpButton is a global variable, right? Don't use global variables. It's way better to create a class which holds your state (can be view model, ...). I'm going to skip a state class in all examples below and will use BOOL helpButtonEnabled property on the same view controller (this is not mandatory, it just makes all these examples a bit shorter). You can move this property elsewhere, it can be a state class, it can be basically any object.
Another thing is this NSTimer, NSTrackingArea, ... With all these things one is wasting CPU cycles, battery life, ... Cocoa & Objective-C offers various ways how to monitor a property value and react to it. You can override property setter, you can use KVO or bindings. All three methods are covered in examples below.
There are other ways for sure (like ReactiveCocoa), but I'd like to demonstrate three ways how to achieve it without dependencies.
Initial state
Imagine you have this view:
With the following implementation:
#import "ViewController.h"
#interface ViewController ()
// Help button from the Main.storyboard
// Imagine it's your m_btHelp
#property (nonatomic, strong) IBOutlet NSButton *helpButton;
// Property driving helpButton enabled/disabled state
// Imagine it's your g_bEnableHelpButton
#property (nonatomic, getter=isHelpButtonEnabled) BOOL helpButtonEnabled;
#end
#implementation ViewController
// Just another button action coming from the Main.storyboard which toggles
// our helpButtonEnabled property value
- (IBAction)toggleHelpButtonEnabled:(id)sender {
self.helpButtonEnabled = !self.helpButtonEnabled;
}
#end
There's help button and there's toggle button which just toggles helpButtonEnabled value (YES -> NO, NO -> YES).
How to monitor it without timer, tracking area, ... to update the help button state?
Override setter
Encapsulating Data.
#implementation ViewController
// This is setter for the helpButtonEnabled property.
- (void)setHelpButtonEnabled:(BOOL)helpButtonEnabled {
// If the new value equals, do nothing
if (helpButtonEnabled == _helpButtonEnabled) {
return;
}
// Update instance variable
_helpButtonEnabled = helpButtonEnabled;
// Update button state
_helpButton.enabled = helpButtonEnabled;
}
- (void)viewDidLoad {
[super viewDidLoad];
// When the view loads update button state to the initial value
_helpButton.enabled = _helpButtonEnabled;
}
// Just another button action coming from the Main.storyboard which toggles
// our helpButtonEnabled property value
- (IBAction)toggleHelpButtonEnabled:(id)sender {
self.helpButtonEnabled = !self.helpButtonEnabled;
}
#end
KVO
Introduction to Key-Value Observing Programming Guide.
static void * const ViewControllerHelpButtonEnabledContext = (void*)&ViewControllerHelpButtonEnabledContext;
#implementation ViewController
- (void)dealloc {
// Remove previously registered observer when the view controller goes away
[self removeObserver:self forKeyPath:#"helpButtonEnabled" context:ViewControllerHelpButtonEnabledContext];
}
- (void)viewDidLoad {
[super viewDidLoad];
// Register observer for the helpButtonEnabled key path
// - it fires immeditately with the current value (NSKeyValueObservingOptionInitial)
// - it fires later every single time new value is assigned (NSKeyValueObservingOptionNew)
// - context is used to quickly distinguish why the observeValueForKeyPath:... was called
[self addObserver:self
forKeyPath:#"helpButtonEnabled"
options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew
context:ViewControllerHelpButtonEnabledContext];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
if (context == ViewControllerHelpButtonEnabledContext) {
// It's our observer, let's update button state
_helpButton.enabled = _helpButtonEnabled;
} else {
// It's not our observer, just forward it to super implementation
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
// Just another button action coming from the Main.storyboard which toggles
// our helpButtonEnabled property value
- (IBAction)toggleHelpButtonEnabled:(id)sender {
self.helpButtonEnabled = !self.helpButtonEnabled;
}
#end
Binding
Introduction to Cocoa Bindings Programming Topics.
#implementation ViewController
- (void)dealloc {
// Remove binding when the view controller goes away
[self.helpButton unbind:NSEnabledBinding];
}
- (void)viewDidLoad {
[super viewDidLoad];
// self.helpButton.enabled is binded to self.helpButtonEnabled
[self.helpButton bind:NSEnabledBinding
toObject:self
withKeyPath:#"helpButtonEnabled"
options:nil];
}
// Just another button action coming from the Main.storyboard which toggles
// our helpButtonEnabled property value
- (IBAction)toggleHelpButtonEnabled:(id)sender {
self.helpButtonEnabled = !self.helpButtonEnabled;
}
#end