objective-c - NSUndoManager 基础知识

Question

我制作了一个带有按钮的应用程序，当您按下它时，它会被禁用，并且撤消操作应该将其返回到之前的状态(启用它)。我使用 NSUndoManager 来实现这一点，但它不起作用。我的应用程序中似乎缺少一些必要的东西，但我找不到具体是什么。

AppDelegate.h:

#import <Cocoa/Cocoa.h>

@interface AppDelegate : NSObject <NSApplicationDelegate>
{
    NSUndoManager* undoManager;
}

@property (assign) IBOutlet NSWindow *window;
@property (weak) IBOutlet NSButton *button;
- (IBAction)Disable:(id)sender;

@end

AppDelegate.m:

#import "AppDelegate.h"

@implementation AppDelegate

@synthesize window = _window;

- (NSUndoManager*)windowWillReturnUndoManager:(NSWindow*)window
{
    return undoManager;
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{

}

- (id) init
{
    if(self = [super init])
        undoManager = [[NSUndoManager alloc]init];
    return self;
}


- (IBAction)Disable:(id)sender
{
    [[undoManager prepareWithInvocationTarget:self]Enable];
    [_button setEnabled:NO];
    if (![undoManager isUndoing])
        [undoManager setActionName:@"Disable"];
}

-(void)Enable
{
    [[undoManager prepareWithInvocationTarget:self]Disable:self];
    [_button setEnabled:YES];
    if (![undoManager isUndoing])
        [undoManager setActionName:@"Enable"];
}
@end

我做错了什么？

Answer 1

我已经编辑了您的代码，希望我的示例对您有所帮助。

如果您仍有问题，请通知我 =)

#import "AppDelegate.h"

@interface AppDelegate ()
{
    NSUndoManager* undoManager;
}
@property (weak) IBOutlet NSWindow *window;
@property (weak) IBOutlet NSButton *button;
@property (weak) IBOutlet NSButton *undoButton;

@end

@implementation AppDelegate

- (NSUndoManager*)windowWillReturnUndoManager:(NSWindow*)window
{
    return undoManager;
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    undoManager = [[NSUndoManager alloc]init];
    [self update];
}

- (IBAction)Disable:(id)sender
{
    [[undoManager prepareWithInvocationTarget:self]Enable];
    [_button setEnabled:NO];
    if (![undoManager isUndoing])
        [undoManager setActionName:@"Disable"];
    [self update];
}

- (IBAction)undo:(id)sender
{
    [undoManager undo];
    [self update];
}

-(void)Enable
{
    [[undoManager prepareWithInvocationTarget:self]Disable:self];
    [_button setEnabled:YES];
    if (![undoManager isUndoing])
        [undoManager setActionName:@"Enable"];
    [self update];
}

- (void)update
{
    self.undoButton.title = [undoManager canUndo]?@"Undo":@"Can't undo";
}

@end