Improve support for 3rd party animatable properties

[hfossli]

Hi

I have a couple of classes and components I very much would like to integrate with Pop. I think it would be awesome to share my latest doings with everyone.

My suggested course of action

1. Create a new project with a podspec named "+Pop"
2. Write a class named "POPAnimatableProperty+"
3. Define all animatable properties in header e.g. "kPOPView"
4. In some way declare all the POPAnimatableProperty so that it is accessible via +[POPAnimatableProperty propertyWithName:]

I'm not quite sure about how to do listpoint 4.

The general question is: How should 3rd party libraries go about integrating with Pop? Some guidelines along the lines of this http://promisekit.org/#adding-promises-to-third-party-libraries would be great!

[kimon]

Looking forward to your writeup. If you'd like to add to the default list of properties provided by POP, here is one user-submitted example: https://github.com/facebook/pop/commit/43a10eee86d1a2ec3ad5617838985ed60e2dda57.

If the property is specific to one of your classes, I would suggest a category extension where you can create and optionally cache your definition. eg

@interface POPAnimatableProperty (MyExtension)
+ (POPAnimatableProperty +)myProperty;
@end

Let me know if you have more questions.

[hfossli]

I've created an extension as you suggested. This works fine for most of the code.

Though there is one problem: One of the properties on my class is a struct. I would like to animate this struct so I've written an NSValue-category which allows me to store those value. When setting the toValue on the animation it throws an exception.

2014-05-13 16:24:04.445 AGGeometryKit+Pop[63142:60b] *** Terminating app due to uncaught exception 'Unsuported value', reason: 'Animating NSConcreteValue values is not supported'
*** First throw call stack:
(
    0   CoreFoundation                      0x01c991e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x01a188e5 objc_exception_throw + 44
    2   CoreFoundation                      0x01c98fbb +[NSException raise:format:] + 139
    3   AGGeometryKit+Pop                   0x0002795a _Z8POPUnboxP11objc_objectR12POPValueTypeRjb + 570
    4   AGGeometryKit+Pop                   0x00041580 -[POPPropertyAnimation setToValue:] + 160

It does not seem straight forward plug in a custom NSValue with POP, unfortunately...

[hfossli]

As a hack I could always store the values in a CATransform3D, but that just feels wrong...

[hfossli]

@kimon Could this be reopened?

[grp]

Right now, Pop only supports animating a subset of structure types, generally the ones included with the system frameworks. I'd file a new issue for supporting additional or arbitrary structure types.

A workaround for now would be to use multiple animations, each with an animatable property that affects one element of your custom structure type. As long as the spring constant / timing function is the same for each animation, they will all run together.

[hfossli]

@grp Yep, that is what I have currently done in https://github.com/hfossli/AGGeometryKit-POP/blob/master/Source/POPAnimatableProperty%2BAGGeometryKit.m

Seems to work allright. I do think the POPCGUtils.h should be public and not private as it is today. Since values_from_point and values_to_point could not only be helpful, but also avoid too loose coupling when writing readBlock and writeBlock in a custom POPAnimatableProperty.

[aleclarson]

I think @hfossli is right when he suggests POPCGUtils.h should be public. The POPCGColor____ methods are valuable for my UILabel.textColor custom animatable property.

[kimon]

Okay :) We wanted to start with the smallest of footprints. Reopening to investigate based on user demand.

[antoinelamy]

I am not sure this is the correct place to talk about it but I am taking a chance. What I want to do is to animate the properties of a custom object and instead of creating individual animations for each properties, I want to be able to pass my entire object as a toValue.

Right now, the library forbid me doing that by raising an exception Animating PPCustomObject values is not supported. By digging a little bit, it seems that the toValue need to be vectorized with the POPVector class. I do not understand this limitation because for a custom property to be animated, it is already required to supply a readBlock that kind of do just that. Why not calling the readBlock on a custom property animation and use the returned array to create a vector?

[leverdeterre]

Hi everybody, i'have a pull request on POP that can improve that. https://github.com/facebook/pop/pull/89

This pull request provide a better understand of the API by using methods :

+ (id)propertyWithCustomName:(NSString *)name;
+ (id)propertyWithCustomName:(NSString *)name initializer:(void (^)(POPMutableAnimatableProperty *prop))block;

[antoinelamy]

@leverdeterre, these new methods seems nice but do not address my point, which is about setting a custom class as a toValue

[ghost]

Thank you for reporting this issue and appreciate your patience. We've notified the core team for an update on this issue. We're looking for a response within the next 30 days or the issue may be closed.