Storing and retrieving a custom object from NSPasteBoard

Question

I have an object that belongs to this class that contains the following declarations:

HEADER

@interface MyClassObject : NSObject <NSCopying, NSPasteboardWriting, NSPasteboardReading>

@property (nonatomic, strong) NSArray *children;
@property (nonatomic, assign) NSInteger type;
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) id node;

children holds other objects of this class, node holds objects that can be NSView or NSImageView.

I would like to be able to copy and paste objects of this type to/from NSPasteboard.

I have google around but the explanations are vague.

What should I do to make this class copiable/readable to NSPasteboard or in other words, make it conform to NSPasteboardWriting and NSPasteboardReading protocols?

I don't have the slightest clue on how this is done and as usual, Apple documetation and nothing is the same thing.

Answer 1

This is the complete solution.

First thing is to make the class conforming to NSCoding too. In that case the class declaration will be

@interface MyClassObject : NSObject <NSCopying, NSPasteboardWriting, NSPasteboardReading, NSCoding>

To make it compatible with NSCoding you have to implement encodeWithCoder: and initWithCoder:... in my case:

- (void)encodeWithCoder:(NSCoder *)coder {

  [coder encodeObject:@(self.type) forKey:@"type"];
  [coder encodeObject:self.name forKey:@"name"];
  // converting the node to NSData... 
  // the object contained in node must be compatible with NSCoding
  NSData *nodeData = [NSKeyedArchiver archivedDataWithRootObject:self.node];
  [coder encodeObject:nodeData forKey:@"node"];

  NSData *childrenData = [NSKeyedArchiver archivedDataWithRootObject:self.children];
  [coder encodeObject:childrenData forKey:@"children"];

}

- (id)initWithCoder:(NSCoder *)coder {

  self = [super init];

  if (self) {

    _type = [[coder decodeObjectForKey:@"type"] integerValue];
    _name = [coder decodeObjectForKey:@"name"];

    NSData *nodeData = [coder decodeObjectForKey:@"node"];
    _efeito = [NSKeyedUnarchiver unarchiveObjectWithData:nodeData];

    NSData *childrenData = [coder decodeObjectForKey:@"children"];
    _children = [NSKeyedUnarchiver unarchiveObjectWithData:childrenData];
    _parent = nil;  // I want this to be nil when the object is recreated
  }

To make the class work with NSPasteboard you have to add these 4 methods:

-(id)initWithPasteboardPropertyList:(id)propertyList ofType:(NSString *)type {
  return [NSKeyedUnarchiver unarchiveObjectWithData:propertyList];
}


+(NSArray *)readableTypesForPasteboard:(NSPasteboard *)pasteboard {
    // I am using the bundleID as a type  
    return @[[[NSBundle mainBundle] bundleIdentifier]];
}

- (NSArray *)writableTypesForPasteboard:(NSPasteboard *)pasteboard {
  // I am using the bundleID as a type  
  return @[[[NSBundle mainBundle] bundleIdentifier]];
}


- (id)pasteboardPropertyListForType:(NSString *)type {
  // I am using the bundleID as a type  
  if(![type isEqualToString:[[NSBundle mainBundle] bundleIdentifier]]) {
    return nil;
  }

  return [NSKeyedArchiver archivedDataWithRootObject:self];
}

Then, on the class you implement the copy and paste you add:

- (void)copy:(id)sender {

  NSPasteboard *pasteBoard = [NSPasteboard generalPasteboard];
  [pasteBoard clearContents];

  NSArray *copiedObjects = @[theObjectYouWantToCopyToThePasteboard];
  [pasteBoard writeObjects:copiedObjects];

}

- (void)paste:sender {

  NSPasteboard *pasteboard = [NSPasteboard generalPasteboard];
  NSArray *classArray = @[[LayerObject class]];
  NSDictionary *options = [NSDictionary dictionary];

  BOOL ok = [pasteboard canReadItemWithDataConformingToTypes:@[[[NSBundle mainBundle] bundleIdentifier]]];

  if (ok) {
    NSArray *objectsToPaste = [pasteboard readObjectsForClasses:classArray options:options];
    MyObjectClass *object = [objectsToPaste objectAtIndex:0];

    // object is the one you have copied to the pasteboard
    // now you can do whatever you want with it.
    // add the code here.    
  }
}