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iOS

Posted by Tom Coomer
Tom Coomer
1,331 Points

Clear NSTextField when in focus (OSX)

I would like the textfield to clear when the user selects it so they can begin typing without needing to delete what is already there. To clear the textfield I have the code below but i am not sure how I detect that it is in focus. Thanks

[myTextField setStringValue: @""];

1 Answer

Robert Bojor
PLUS
Robert Bojor
Courses Plus Student 29,439 Points
Robert Bojor
Robert Bojor
Courses Plus Student 29,439 Points

Hi Tom,

You could use NSTextFieldDelegate and implement a mix of controlTextDidChange:, control:textShouldBeginEditing: and control:textShouldEndEditing: methods like in the code below. 

// RBAppDelegate.h
#import <Cocoa/Cocoa.h>
@interface RBAppDelegate : NSObject <NSApplicationDelegate, NSTextFieldDelegate>
@property (assign) IBOutlet NSWindow *window;
@end

// RBAppDelegate.m
#import "RBAppDelegate.h"

@interface RBAppDelegate()
@property (nonatomic) BOOL isEditing;
@end

@implementation RBAppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    _isEditing = NO;
}

- (void)controlTextDidChange:(NSNotification *)notification {
    NSTextField *textField = [notification object];
    NSString *stringVal = [textField stringValue];
    if (_isEditing) {
        [textField setStringValue:[stringVal substringFromIndex:[stringVal length]-1]];
        _isEditing = NO;
    }
}

- (BOOL)control:(NSControl *)control textShouldBeginEditing:(NSText *)fieldEditor {
    _isEditing = YES;
    return true;
}
-(BOOL)control:(NSControl *)control textShouldEndEditing:(NSText *)fieldEditor {
    _isEditing = NO;
    return true;
}
@end

When you start typing inside the NSText the control:textShouldBeginEditing: is fired first. If you use this method to clear out your text field you will lose your first letter that was pressed, which is not very nice...

However, the controlTextDidChange: is fired every time you press a key inside the NSText field but the value of the text field is already updated to include the pressed key. Using the _isEditing bool we can test is the editing has begun, set the text field value to the last key that was pressed - using the substringFromIndex: method - and reset the _isEditing back to false so on the next key press nothing affects the text field value.

Hope this helped. Cheers!

Tom Coomer
Tom Coomer
1,331 Points

Thank you