Tagging CALayers in iPhone

Question

I am looking for a general way to be able to search for a unique CALayer in a hierarchy without having to remember where the layer is in a hierarchy (and use the sublayer: and superlayer: methods).

I know this is possible with UIViews (which makes flipping views easy) but is it possible for CALayer?

thank you in advance for your help

Peyman

score 61 · Answer 1 · edited Nov 07 '11 at 07:26

61

You can also use the name property of the CALayer.

[layer setName:@"myKey"];

To look it up,

- (CALayer *)myLayer {

    for (CALayer *layer in [superLayerOfMyLayer sublayers]) {

            if ([[layer name] isEqualToString:LabelLayerName]) {
                return layer;
            }
    }

    return nil;
}

edited Nov 07 '11 at 07:26

EmptyStack

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answered Nov 11 '10 at 03:01

Mshah2

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1

Hmm. No way to get a layer by name other than walking 'em all? Ahh well, it's better than nothing! – Joe D'Andrea Oct 09 '12 at 20:10
1

Could use a property to avoid having to I suppose. It'd be nice to have a way to look it up though. – Adam Waite Sep 01 '14 at 12:02

score 23 · Answer 2 · answered May 18 '10 at 02:05

Apologize. I was being a dunce. CALayer is a key-value coding compliant container so I can create arbitrary values (including tags) in any instance. To create a tag for instance we do:

[rootLayer setValue:[NSNumber numberWithInt:101] forKey:@"PFtag"];

thank you

score 11 · Answer 3 · answered Feb 13 '18 at 05:31

11

In Swift you can do this

let layer = CAShapeLayer()
layer.name = "\(index)"

Then to get the layers you can do this

for item in self.layer.sublayers! {
    if item.name == "\(index)" {
        item.removeFromSuperlayer()
        item.removeAllAnimations()
    }
}

answered Feb 13 '18 at 05:31

Anirudha Mahale

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It'd be more idiomatic these days to use a where clause on your loop, rather than the if statement: `for item in self.layer.sublayers! where item.name == "\(index)"`. Also probably preferable to not use force unwraps, but that's more subjective. – Sam Jul 05 '20 at 18:54
I prefer ```self.layer.sublayers?.filter({ $0.name == "xxx" }).forEach..``` – woheras Jul 28 '22 at 10:34

score 6 · Answer 4 · answered Jan 07 '19 at 01:07

6

A modern safe take on this.

Assign a name to the layer:

layer.name = "MyLayer"

Then, filter through all sublayers searching for the name:

layer.sublayers?
    .filter { layer in return layer.name == "MyLayer" }
    .forEach { layer in
        layer.removeFromSuperlayer()
        layer.removeAllAnimations()
}

answered Jan 07 '19 at 01:07

CodeBender

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Nice solution! I think you can replace `layer in return layer.name == "MyLayer"` with `$0.name == "MyLayer"`. – koen Jan 01 '20 at 22:12
1

Thanks @koen That is definitely valid, but sometimes I do prefer the clarity of naming it over using the $0. However, both work fine & just comes down to developer preference / enforced style (if applicable) – CodeBender Jan 01 '20 at 23:16

score 3 · Answer 5 · answered Mar 27 '20 at 00:57

First, you need to name your CALayer:

    let shadowLayer = CALayer()
    shadowLayer.name = "myname"

After, you just do a search by name:

    if let neuBlackLayer = layer.sublayers?.first(where: { $0.name == "myname" }) {
       // do something with your layer
    }

same with guard:

    guard let neuBlackLayer = layer.sublayers?.first(where: { $0.name == "myname" }) else { return }
    // do something with your layer

Added this answer to clarify other's answers:

It is clear, no need to filter or loops.
It does what asked in question: the way to find a unique layer (there is nothing about removing it from superlayers, etc. )
It is written using Swift 5.1

Tagging CALayers in iPhone

5 Answers5

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