Pasteboards and Nil-Targeted Actions(Chapter 21 of Cocoa Programming for Mac OS

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1 - (void)writeToPasteboard:(NSPasteboard *)pb
2 {
3     [pb declareTypes:[NSArray arrayWithObject:NSStringPboardType] owner:self];
4     [pb setString:string forType:NSStringPboardType];
5 }
6
7 - (BOOL)readFromPasteboard:(NSPasteboard *)pb
8 {
9     NSArray *types = [pb types];
10     if([types containsObject:NSStringPboardType])
11     {
12         NSString *value = [pb stringForType:NSStringPboardType];
13         if([value length] == 1)
14         {
15             [self setString:value];
16             return YES;
17         }
18     }
19     
20     return NO;
21 }
22
23 - (IBAction)cut:(id)sender
24 {
25     [self copy:sender];
26     [self setString:@""];
27 }
28
29 - (IBAction)copy:(id)sender
30 {
31     NSPasteboard *pb = [NSPasteboard generalPasteboard];
32     [self writeToPasteboard:pb];
33 }
34
35 - (IBAction)paste:(id)sender
36 {
37     NSPasteboard *pb = [NSPasteboard generalPasteboard];
38     if (![self readFromPasteboard:pb])
39     {
40         NSBeep();
41     }
42 }