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Add a polyfill for Objective-C to select TZStackView only when UIStackView is unavailable.
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‎Polyfill/UIStackView+TZStackView.h‎

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//
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// UIStackView+TZStackView.h
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// FitStar
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//
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// Created by Frederic Barthelemy on 9/9/15.
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// Copyright © 2015 FitStar. All rights reserved.
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//
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#import <UIKit/UIKit.h>
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// You probably want the real UIStackView!
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#import <UIKit/UIStackView.h>
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// Define a preprocessor macro to coopt all your references to UIStackView with this class.
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#define UIStackView _polyfill_UIStackView
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/**
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This class is a polyfill. Go look at UIStackView.h or TZStackView.swift for implementation details.
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Usage: Include this in your Prefix.pch, and use UIStackView * everywhere as if you were on iOS 9.0
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This class works by overriding +(instancetype)alloc to dynamically alloc the appropriate class.
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Additionally it defines a PreProcessor macro that will replace all your uses of UIStackView with this class.
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@warning: Dynamic tricks like NSStringFromClass([UIStackView class]) will probably not do what you want. Also, the only supported class method is `alloc`.
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All methods defined here are simply stubs to silence the compiler, since you can't ever alloc an instance of this.
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*/
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@interface _polyfill_UIStackView : UIView
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#pragma mark - Everything below here is copied in from UIStackView.h -
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/* UIStackView enforces that all views in the arrangedSubviews list
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must be subviews of the UIStackView.
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Thus, when a view is added to the arrangedSubviews, UIStackView
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adds it as a subview if it isn't already. And when a view in a
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UIStackView's arrangedSubviews list receives -removeFromSuperview
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it is also removed from the arrangedSubviews.
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*/
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- (instancetype)initWithArrangedSubviews:(NSArray<__kindof UIView *> *)views; // Adds views as subviews of the receiver.
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@property(nonatomic,readonly,copy) NSArray<__kindof UIView *> *arrangedSubviews;
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/* Add a view to the end of the arrangedSubviews list.
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Maintains the rule that the arrangedSubviews list is a subset of the
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subviews list by adding the view as a subview of the receiver if
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necessary.
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Does not affect the subview ordering if view is already a subview
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of the receiver.
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*/
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- (void)addArrangedSubview:(UIView *)view;
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/* Removes a subview from the list of arranged subviews without removing it as
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a subview of the receiver.
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To remove the view as a subview, send it -removeFromSuperview as usual;
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the relevant UIStackView will remove it from its arrangedSubviews list
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automatically.
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*/
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- (void)removeArrangedSubview:(UIView *)view;
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/*
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Adds the view as a subview of the container if it isn't already.
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Updates the stack index (but not the subview index) of the
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arranged subview if it's already in the arrangedSubviews list.
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*/
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- (void)insertArrangedSubview:(UIView *)view atIndex:(NSUInteger)stackIndex;
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/* A stack with a horizontal axis is a row of arrangedSubviews,
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and a stack with a vertical axis is a column of arrangedSubviews.
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*/
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@property(nonatomic) UILayoutConstraintAxis axis;
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/* The layout of the arrangedSubviews along the axis
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*/
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@property(nonatomic) UIStackViewDistribution distribution;
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/* The layout of the arrangedSubviews transverse to the axis;
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e.g., leading/trailing edges in a vertical stack
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*/
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@property(nonatomic) UIStackViewAlignment alignment;
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/* Spacing between adjacent edges of arrangedSubviews.
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Used as a strict spacing for the Fill distributions, and
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as a minimum spacing for the EqualCentering and EqualSpacing
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distributions. Use negative values to allow overlap.
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*/
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@property(nonatomic) CGFloat spacing;
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/* Baseline-to-baseline spacing in vertical stacks.
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The baselineRelativeArrangement property supports specifications of vertical
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space from the last baseline of one text-based view to the first baseline of a
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text-based view below, or from the top (or bottom) of a container to the first
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(or last) baseline of a contained text-based view.
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This property is ignored in horizontal stacks. Use the alignment property
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to specify baseline alignment in horizontal stacks.
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Defaults to NO.
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*/
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@property(nonatomic,getter=isBaselineRelativeArrangement) BOOL baselineRelativeArrangement;
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/* Uses margin layout attributes for edge constraints where applicable.
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Defaults to NO.
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*/
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@property(nonatomic,getter=isLayoutMarginsRelativeArrangement) BOOL layoutMarginsRelativeArrangement;
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@end

‎Polyfill/UIStackView+TZStackView.m‎

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//
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// UIStackView+TZStackView.m
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// FitStar
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//
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// Created by Frederic Barthelemy on 9/9/15.
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// Copyright © 2015 FitStar. All rights reserved.
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//
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#import <objc/runtime.h>
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#import "FitStar-Swift.h"
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#import "UIStackView+TZStackView.h"
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#if __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_9_0
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#error UIStackView+TZStackView Polyfill is no longer required! Remove these files. Congratulations!
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#endif
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@implementation _polyfill_UIStackView
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+ (instancetype)alloc {
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// Actually pick the best StackView implementation:
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return [NSClassFromString(@"UIStackView") alloc] ?: [TZStackView alloc];
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}
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#pragma mark - Polyfill Stubs
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- (instancetype)initWithArrangedSubviews:(NSArray<__kindof UIView *> *)views FIT_UNAVAILABLE(@"Polyfill Stub",@"You can't actually have an instance of this object.");
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- (void)addArrangedSubview:(UIView *)view FIT_UNAVAILABLE(@"Polyfill Stub",@"You can't actually have an instance of this object.");
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- (void)removeArrangedSubview:(UIView *)view FIT_UNAVAILABLE(@"Polyfill Stub",@"You can't actually have an instance of this object.");
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- (void)insertArrangedSubview:(UIView *)view atIndex:(NSUInteger)stackIndex FIT_UNAVAILABLE(@"Polyfill Stub",@"You can't actually have an instance of this object.");
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@end

‎README.md‎

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@@ -7,6 +7,7 @@ A wonderful layout component called the [`UIStackView` was introduced with *iOS
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- ✅ Compatible with **iOS 7.x** and **iOS 8.x**
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- ✅ Supports the complete API of `UIStackView` including **all** *distribution* and *alignment* options
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- ✅ Supports animating the `hidden` property of the *arranged subviews*
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- ✅ Optional [Polyfill](#polyfill) for Objective-C code to use the name UIStackView, while dynamically selecting TZStackView when on earlier iOS versions.
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- ❌ Supports *Storyboard*
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So this implementation does **not** support Storyboard. It is meant for iOS developers who, like me, want to use the `UIStackView` in our existing apps and like to layout their components in code as opposed to using *Storyboard*.
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```
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![TZStackView hidden animation example](/assets/TZStackView-hide-animation.gif)
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## Polyfill
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(Objective-C only)
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If you're writing code with Objective-C, and you want to dynamically select UIStackView over TZStackView when on iOS versions that provide it, check out [UIStackView+TZStackView](./Polyfill/)
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If you include these files in your project, and include the header in your Prefix.pch, along with TZStackView [see Setup](#setup) you to will be able to type `UIStackView` and have the code dynamically select the right class to fulfill your needs.
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If you go down this route, you don't have to do anything to migrate to UIStackView, but to remove TZStackView.
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Example:
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```objc
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UIStackView * stack = [[UIStackView alloc] initWithArrangedSubviews:@[/*…*/]];
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````
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More documentation in [UIStackView+TZStackView.h](./Polyfill/TZStackView.h)
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## Migrating to UIStackView
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If at a later point you decide to make *iOS 9* the minimum requirement of your app (it will happen sooner or later), you will want to migrate to the real `UIStackView` instead of using this implementation. Because the `TZStackView` is a drop-in replacement for `UIStackView`, you simply replace:
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