NSUndoManager的一点学习记录

来源：互联网发布：明朝朝鲜知乎编辑：程序博客网时间：2024/05/04 07:59

这两天看了一个coredata的官方代码,发现了里面的NSUndoManager类,就稍微的研究了一下.下面是我的一点学习记录

NSUndoManager 说白了主要就是2个方法,一个是redo,一个是undo,也就是对程序的撤销和恢复

-(void)undo{    [self.undoManage undo];}-(void)redo{    [self.undoManage redo];}

它里面有一个prepareWithInvocationTarget方法需要注意, 当进行操作时，控制器会添加一个该操作的逆操作的invocation到Undo栈中。当进行Undo操作时，Undo操作的逆操作会倍添加到Redo栈中，就这样利用Undo和Redo两个堆栈巧妙的实现撤销操作。

这里需要注意的是，堆栈中存放的都是NSInvocation实例。

还有就是setLevelsOfUndo方法,它设定了你最多可以撤销的次数

下面是一个从网上看到的源码,以供参考

-(void)undo{    [self.undoManage undo];}-(void)redo{    [self.undoManage redo];}-(void)apper{        if (!num) {        self.navigationItem.rightBarButtonItem=nil;    }    else    {        if (self.undoManage.canUndo) {            UIBarButtonItem*right=[[UIBarButtonItem alloc] initWithTitle:@"undo" style:UIBarButtonItemStyleBordered target:self action:@selector(undo)];            self.navigationItem.rightBarButtonItem=right;            [right release];        }    }    if (!num) {        self.navigationItem.leftBarButtonItem=nil;    }    else    {        UIBarButtonItem*left=[[UIBarButtonItem alloc] initWithTitle:@"redo" style:UIBarButtonItemStyleBordered target:self action:@selector(redo)];        self.navigationItem.leftBarButtonItem=left;        [left release];            }}-(void)sub{    num-=10;    [[self.undoManage prepareWithInvocationTarget:self] add];    label.text=[NSString stringWithFormat:@"%d",num];    [self apper];    }-(void)add{    num+=10;    [[self.undoManage prepareWithInvocationTarget:self] sub];    label.text=[NSString stringWithFormat:@"%d",num];    [self apper];}#pragma mark - View lifecycle- (void)viewDidLoad{    [super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.    label=[[UILabel alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];    UIButton*btn=[UIButton buttonWithType:UIButtonTypeRoundedRect];    btn.frame=CGRectMake(150, 150, 100, 100);    [btn setTitle:@"add" forState:UIControlStateNormal];    [btn addTarget:self action:@selector(add) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:btn];    [self.view addSubview:label];    num=0;    label.text=[NSString stringWithFormat:@"%d",num];    undoManage=[[NSUndoManager alloc] init];    [self.undoManage setLevelsOfUndo:999];}

有一篇不错的参考文章:IOS开发之Cocoa编程—— NSUndoManager

0 0