I´m newbie with cocoa. I have a button and a textField in my app. I want the button disabled when the textfield is empty and enabled when the user type something.
Any point to start? Any "magic" binding in Interface Builder?
Thanks
[EDITED]
I´ve tried to set the appDelegate as the NSTextfield´s delegate and added this method (myTextfield and myButton are IBOutlets):
- (void)textDidChange:(NSNotification *)aNotification
{
if ([[myTextField stringValue]length]>0) {
[myButton setEnabled: YES];
}
else {
[myButton setEnabled: NO];
}
}
But nothing happens...
I´ve tried to set the appDelegate as the NSTextfield´s delegate and added this method (myTextfield and myButton are IBOutlets):
- (void)textDidChange:(NSNotification *)aNotification
{
if ([[myTextField stringValue]length]>0) {
[myButton setEnabled: YES];
}
else {
[myButton setEnabled: NO];
}
}
That's the hard way, but it should work just fine. Either you haven't hooked up the text field's delegate outlet to this object, you haven't hooked up the myTextField outlet to the text field, or you haven't hooked up the myButton outlet to the button.
The other way would be to give the controller a property exposing the string value, bind the text field's value binding to this stringValue property, and bind the button's enabled binding to the controller's stringValue.length.
You could also give the controller two properties, one having a Boolean value, and set that one up as dependent upon the string property, and bind the button to that. That's a cleaner and possibly more robust solution, though it is more work.
Here's a solution using bindings.
Below I setup a NSTextField that is bound to the file owner's "text" property. "text" is a NSString. I was caught by "Continuously Updates Value". Thinking my solution didn't work but really it wasn't updating as the user typed, and only when the textfield lost focus.
And now setting up bindings on the button, simply set its enabled state to the length of the file owner's text property.
Annd, the working product.
If you use controlTextDidChange instead of textDidChange, you can get rid of the notification stuff and just rely on being the NSTextField's delegate.
Thanks Peter. What I missed (in my hard way version) is this piece of code in the awakeFromNib in the appDelegate:
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self selector:#selector(textDidChange:) name:NSControlTextDidChangeNotification object:myTextField];
It works perfect. Now I´m trying the easy way, but I´m afraid I´m not still good enough with the bindings.
To bind the property
#property (retain) IBOutlet NSString *aStringValue;
with the textfield´s value, what I have to use in IB for "Bind to:", "Controller Key" and "Model Key Path"?
Related
I have a TextField in my Cocoa application. This TextField will be sometimes filled and sometimes empty.
I want it so that when the field is empty a button is disabled. Now I check the field whenever I do some action with Core Data from where the TextField gets its value.
I'd like for it to always be checked for this.
If the user edits the text field and brings up the field editor then you can use the following.
You can implemented the NSTextFieldDelegate protocol (which is really just the NSControlTextEditing protocol). For example, in a controller or a delegate object implement the control:textShouldEndEditing: method and use this to check the values of the new string. If the string is empty then disable the button.
// In a control object which has a reference to the NSTextField and the NSButton
- (BOOL)control:(NSControl *)control textShouldEndEditing:(NSText *)fieldEditor {
if ([fieldEditor.string isEqualToString:#""])
{
[self.button setEnabled:NO];
return YES;
}
[self.button setEnabled:YES];
return YES;
}
Update: Sorry missed that bit about CodeData. In this case you should follow the instructions here, Disable/Enable NSButton if NSTextfield is empty or not,
The other way would be to give the controller a property exposing the
string value, bind the text field's value binding to this stringValue
property, and bind the button's enabled binding to the controller's
stringValue.length.
#interface MyClass {
NSString *_myString;
}
#property (copy) *myString;
#end
#implementation MyClass
#synthesize myString = _myString;
- (void)awakeFromNib {
self.myString = #"";
}
In the nib, I have an NSTextField and an NSButton. The text field's Value binding is set to myClass.myString. I verified that the variable _myString is being updated correctly when text is typed into the text field.
The Enabled binding of the NSButton is set to myClass.myString.length. However, when I start up the program, the NSButton is enabled! If I go to the textfield and type something into it, the button stays enabled. Then if I erase the text from the textfield, the button becomes disabled.
But why isn't the button disabled to begin with, after the call in awakeFromNib ? Do I have to do some additional work to make the binding work in the opposite direction (myClass.myString --> NSTextField) ? I thought that declaring myString as a property would do the trick.
I'm not sure what is causing this but I would say the easiest way to fix it, since your text will start out empty, is in awakeFromNib do something like [myButton setEnabled:false];
This is my situation in Xcode Interface Builder:
There is also an NSArrayController in entity mode which controls the content of the NSTableView. I want to enable the 'Create' button when the NSTableView is empty (as controlled by the NSSearchField) AND when the text in the NSSearchField is not empty. How do I achieve that? Is it possible without programming?
To what KVO compliant values can I bind the 2 enabled conditions of the 'Create' button?
I don't think there's a way to do it entirely in interface builder, but with a small amount of code you can get it working pretty easily. First, make sure your controller (or App Delegate) is set as the delegate of the search field, and that it has IBOutlet connections to the search field, the button and the array controller. Here's how I would implement it:
// This is an arbitrary pointer to indicate which property has changed.
void *kObjectsChangedContext = &kObjectsChangedContext;
- (void)awakeFromNib {
// Register as an observer so we're notified when the objects change, and initially at startup.
[arrayController addObserver:self
forKeyPath:#"arrangedObjects"
options:NSKeyValueObservingOptionInitial
context:kObjectsChangedContext];
}
// This updates the button state (based on your specs)
- (void)updateButton {
BOOL canCreate = (searchField.stringValue.length > 0 &&
0 == [arrayController.arrangedObjects count]);
[createButton setEnabled:canCreate];
}
// This delegate method is called whenever the text changes; Update the button.
- (void)controlTextDidChange:(NSNotification *)obj {
[self updateButton];
}
// Here's where we get our KVO notifications; Update the button.
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if (kObjectsChangedContext == context)
[self updateButton];
// It's good practice to pass on any notifications we're not registered for.
else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
If you're new to bindings some of that may look like Greek, hopefully the comments are clear enough.
I'm SOOO late for this, but came up with another method and just tested it in my app. It works, so I'm going to share it for anyone who will find this question in the future.
Basically what you want to do is to create a property WITHOUT a corresponding value in your controller
#property (readonly) BOOL enableProperty;
This means that there's actually no
BOOL enableProperty;
defined in the header file, or anywhere
then, rather than synthesize it, just write your own getter, and put there your condition
- (BOOL) enableProperty{
return (condition);
}
Third step: anytime there's the chance that your condition changes, notify it.
- (void) someMethod{
//.... Some code
[self willChangeValueForKey:#"enableProperty"];
[Thisline mightChange:theCondition];
[self didChangeValueForKey:#"enableProperty"];
//.... Some other code
}
fourth step: in IB, bind your control's enabled property to this "fake" property.
Enjoy! ;)
You seems to have a window, so presumably you have a controller object which is set as the File's Owner for the NIB file.
Why not declare a boolean property in this controller class, that returns a value based whatever conditions you want ?
#property(readonly) BOOL canCreate;
That you implement :
-(BOOL)canCreate {
// compute and return the value
}
Be sure to send KVO notifications appropriately when the conditions for the creation change.
The last step is to bind the button's enabled binding on the File's Owner canCreate key.
I want to show an NSPopover from an NSToolbarItem button in my toolbar.
(i.e. positioned below the button).
Ideally, I want to pass the NSView of the button to the popover to position it.
My question is, how do I get the NSView of the NSToolbarItem?
[toolbarbutton view] always returns nil.
The answer appears to be in the video for the 2011 WWDC Session 113, "Full Screen and Aqua Changes." Basically, put an NSButton inside the NSToolbaritem and use the view of that.
A blog post is here: http://www.yellowfield.co.uk/blog/?p=33, and a sample project is on github at http://github.com/tevendale/ToolbarPopover
All in the sprit of http://xkcd.com/979!
You can send the action directly from the NSButton enclosed in the NSToolbarItem (which is what you should generally do anyways, consider segmented controls, where each segment has its own target/action), and that will do the trick.
Instead of getting the view from the IBAction sender, connect an IBOutlet directly to the toolbar item and use that to get the relative view:
In your header file:
#property (weak) IBOutlet NSToolbarItem *theToolbarItem;
#property (weak) IBOutlet NSPopover *thePopover;
In your implementation file, to show the popover:
[self.thePopover showRelativeToRect:[[self.theToolbarItem view] bounds] ofView:[self.theToolbarItem view] preferredEdge:NSMinYEdge];
This will also work for showing popups from menu item selections inside a toolbar item.
While I did achieve that the Popover was shown using the approach mentioned by Stuart Tevendale, I did run into problems when I tried to validate (enable / disable) the NSToolbarItems using the NSToolbarDelegate:
-(BOOL)validateToolbarItem:(NSToolbarItem *)toolbarItem {
BOOL enable = YES;
NSString *identifier = [toolbarItem itemIdentifier];
// This does never get called because I am using a button inside a custom `NSToolbarItem`
if ([identifier isEqualToString:#"Popover"]) {
return [self someValidationMechanism];
}
// For this the validation works when I am using a standard `NSToolbarItem`
else if ([identifier isEqualToString:#"StandardToolbarItem"]){
return [self someOtherValidationMechanism];
}
return enable;
}
So I would advise not to display a Popover from NSToolbarItem. An alternative might be to show a Page Sheet: How to show a NSPanel as a sheet
In IB it is easy to bind a label or text field to some controller's keyPath.
The NSDockTile (available via [[NSApp dockTile] setBadgeLabel:#"123"]) doesn't appear in IB, and I cannot figure out how to programmatically bind its "badgeLabel" property like you might bind a label/textfield/table column.
Any ideas?
NSDockTile doesn't have any bindings, so your controller will have to update the dock tile manually. You could do this using KVO which would have the same effect as binding it.
Create a context as a global:
static void* MyContext=(void*)#"MyContext";
Then, in your init method:
[objectYouWantToWatch addObserver:self forKeyPath:#"dockTileNumber" options:0 context:MyContext];
You then have to implement this method to be notified of changes to the key path:
- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if (context == MyContext) {
[[NSApp dockTile] setBadgeLabel:[object valueForKeyPath:keyPath]];
}
else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
Make sure you remove the observer when the controller object goes away.
If NSDockTile does support bindings, you can use the method bind:toObject:withKeyPath:options: to set up bindings on the badgeLabel property. Check the documentation for details on which arguments to use. If it doesn't work, you could either implement key value observing in your controller class and update the label each time the value changes, or even override NSDockTile to create a bindings compatible subclass.
I've tried lots of variations of bind:toObject:withKeyPath:options: on NSDockTile, on a controller, on the data source. I can't figure out a combination that works. Alternately, is there a way of having a BatchController object that can be bound to the data source, and it then updates the badge? How do I take an NSObject and make it bindable?