How do I animate a UIView with TweenKit?

Use InterpolationAction with tweenable types like CGRect or CGPoint. For example, animate a view's frame by specifying from and to rects with easing, as shown in the basic tween example in the README.

Is TweenKit compatible with SwiftUI?

TweenKit is primarily designed for UIKit. To use it with SwiftUI, you need to wrap animations in UIViewRepresentable, which adds complexity compared to native SwiftUI animation modifiers.

TweenKit vs UIView animations: which is better?

TweenKit offers more control with scrubbable, composable animations for complex sequences, while UIView.animate is simpler for basic tasks. Choose TweenKit for interactive or multi-step animations beyond UIKit's built-in capabilities.

Can TweenKit animate along a custom path?

Yes, use BezierAction to animate objects along Bézier paths with rotation support. The README demonstrates this with a rocket moving along a path, updating both position and transform.

How do I chain multiple animations in TweenKit?

Use ActionSequence to run animations in order. Create individual InterpolationActions and combine them into a sequence, as shown in the moveTwice example where two frame animations run consecutively.

What's the performance like with many animations?

TweenKit runs on Core Animation and is efficient for typical use cases, but the ActionScheduler overhead might impact performance with hundreds of concurrent animations, requiring careful management.

Open-Awesome

TweenKit

MITSwift1.0.3

A powerful, scrubbable animation library for iOS in Swift that can tween any value.

GitHub

1.4k stars79 forks0 contributors

What is TweenKit?

TweenKit is an animation library for iOS written in Swift that allows developers to animate (or 'tween') any value by conforming to the Tweenable protocol. It solves the problem of creating complex, interactive animations with features like scrubbability, grouping, and sequencing, making it easier to build polished user interfaces and onboarding flows.

Target Audience

iOS developers who need to create custom, interactive animations beyond basic UIView animations, particularly those building onboarding experiences, games, or highly dynamic UIs.

Value Proposition

Developers choose TweenKit for its flexibility in animating any type, its scrubbable animations for interactive experiences, and its composable action system that simplifies building complex animation sequences without external dependencies.

Overview

Animation library for iOS in Swift

Use Cases

Best For

Creating interactive onboarding tutorials with scrubbable animations
Building custom activity indicators with arc-based motion
Animating UI elements along Bézier paths with rotation
Developing complex animation sequences with grouping and repeating
Tweening non-standard types like strings or custom objects
Implementing yoyo or reversible animations for playful interactions

Not Ideal For

Projects exclusively using SwiftUI and preferring native declarative animations
Apps needing only simple, one-off UIView animations with AutoLayout
Real-time games requiring physics-based or frame-by-frame animation control
Teams prioritizing minimal dependencies and avoiding third-party libraries

Pros & Cons

Pros

Protocol-Based Extensibility

Any type can be animated by conforming to Tweenable, as demonstrated with examples animating strings like 'bat' to 'cat', enabling custom object tweening beyond standard UI properties.

Scrubbable for Interactivity

Actions can be manually scrubbed using ActionScrubber, ideal for interactive tutorials or progress-based UIs, shown with slider callbacks to control animation progress.

Composable Action System

Animations are built from small, combinable Actions that can be grouped, sequenced, repeated, or reversed, enabling complex sequences like staggered arc animations for activity indicators without boilerplate.

Rich Easing and Paths

Includes built-in easing curves like exponential and elastic, plus arc and bezier path animations with rotation support, as shown in rocket and circular motion examples.

Cons

UIKit-Centric Design

The library is built around UIKit and Core Animation, with no explicit SwiftUI support, requiring extra work via UIViewRepresentable for modern iOS apps adopting SwiftUI.

Imperative API Overhead

Requires manual management of ActionScheduler and explicit animation definitions, which can be more verbose and error-prone than declarative frameworks like SwiftUI animations.

Limited AutoLayout Integration

Animations focus on direct property tweening (e.g., frame, center) rather than AutoLayout constraints, making it less suitable for responsive UI designs without additional constraint manipulation.

Frequently Asked Questions

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