- (void)viewDidLoad {

[superviewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

undoManager= [[NSUndoManageralloc]init];

_a=0;

}

-(void)setvalue:(NSString*)some

{

[undoManagerregisterUndoWithTarget:selfselector:@selector(setvalue:)object:self.label.text];

//或者[[_undomanager prepareWithInvocationTarget:self] setvalue:self.label.text];

[self.labelsetText:some];

_a= [self.label.textintegerValue];

}

- (IBAction)add:(id)sender {

_a++;

[selfsetvalue:[NSStringstringWithFormat:@"%ld",(long)_a]];

}

- (IBAction)undo:(id)sender {

[undoManagerundo];

}

- (IBAction)redo:(id)sender {

[undoManagerredo];

}