MDCSwipeToChoose

Swipe to "like" or "dislike" any view, just like Tinder.app. Build a flashcard app, a photo viewer, and more, in minutes, not hours!

Use UIView+MDCSwipeToChoose to add a swipe gesture and callbacks to any UIView.
Use MDCSwipeToChooseView to get a UI nearly identical to Tinder.app in just a few lines of code.

You may view slides on some the architecture decisions that went into this library here.

How to Install via CocoaPods

Place the following in your Podfile and run pod install:

pod "MDCSwipeToChoose"

How to Use

Check out the sample app for an example of how to use MDCSwipeToChooseView to build the UI in the GIF above.

NOTE: You must run pod install in the Examples/LikedOrNope directory before building the example app.

Every public class contains documentation in its header file.

Swiping Yes/No

The following is an example of how you can use MDCSwipeToChooseView to display a photo. The user can choose to delete it by swiping left, or save it by swiping right.

Objective-C

#import <MDCSwipeToChoose/MDCSwipeToChoose.h>

// ... in a view controller

#pragma mark - Creating and Customizing a MDCSwipeToChooseView

- (void)viewDidLoad {
    [super viewDidLoad];

    // You can customize MDCSwipeToChooseView using MDCSwipeToChooseViewOptions.
    MDCSwipeToChooseViewOptions *options = [MDCSwipeToChooseViewOptions new];
    options.likedText = @"Keep";
    options.likedColor = [UIColor blueColor];
    options.nopeText = @"Delete";
    options.onPan = ^(MDCPanState *state){
        if (state.thresholdRatio == 1.f && state.direction == MDCSwipeDirectionLeft) {
            NSLog(@"Let go now to delete the photo!");
        }
    };

    MDCSwipeToChooseView *view = [[MDCSwipeToChooseView alloc] initWithFrame:self.view.bounds
                                                                     options:options];
    view.imageView.image = [UIImage imageNamed:@"photo"];
    [self.view addSubview:view];
}

#pragma mark - MDCSwipeToChooseDelegate Callbacks

// This is called when a user didn't fully swipe left or right.
- (void)viewDidCancelSwipe:(UIView *)view {
    NSLog(@"Couldn't decide, huh?");
}

// Sent before a choice is made. Cancel the choice by returning `NO`. Otherwise return `YES`.
- (BOOL)view:(UIView *)view shouldBeChosenWithDirection:(MDCSwipeDirection)direction {
    if (direction == MDCSwipeDirectionLeft) {
        return YES;
    } else {
        // Snap the view back and cancel the choice.
        [UIView animateWithDuration:0.16 animations:^{
            view.transform = CGAffineTransformIdentity;
            view.center = [view superview].center;
        }];
        return NO;
    }
}

// This is called then a user swipes the view fully left or right.
- (void)view:(UIView *)view wasChosenWithDirection:(MDCSwipeDirection)direction {
    if (direction == MDCSwipeDirectionLeft) {
        NSLog(@"Photo deleted!");
    } else {
        NSLog(@"Photo saved!");
    }
}

As of version 0.2.0, you may also swipe a view programmatically:

[self.swipeToChooseView mdc_swipe:MDCSwipeDirectionLeft];

Swift

To use objective-c code from swift, you need to use bridging-header.

#ifndef BridgingHeader_h
#define BridgingHeader_h

#import <UIKit/UIKit.h>
#import <MDCSwipeToChoose/MDCSwipeToChoose.h>

#endif

import UIKit

// ... in a view controller that confirms to MDCSwipeToChooseDelegate protocol

override func viewDidLoad() {
    super.viewDidLoad()

    var options = MDCSwipeToChooseViewOptions()
    options.delegate = self
    options.likedText = "Keep"
    options.likedColor = UIColor.blueColor()
    options.nopeText = "Delete"
    options.onPan = { state -> Void in
        if state.thresholdRatio == 1 && state.direction == MDCSwipeDirection.Left {
            println("Photo deleted!")
        }
    }

    var view = MDCSwipeToChooseView(frame: self.view.bounds, options: options)
    view.imageView.image = UIImage(named: "photo.png")
    self.view.addSubview(view)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

// This is called when a user didn't fully swipe left or right.
func viewDidCancelSwipe(view: UIView) -> Void{
    println("Couldn't decide, huh?")
}

// Sent before a choice is made. Cancel the choice by returning `false`. Otherwise return `true`.
func view(view: UIView, shouldBeChosenWithDirection: MDCSwipeDirection) -> Bool{
    if (shouldBeChosenWithDirection == MDCSwipeDirection.Left) {
        return true;
    } else {
        // Snap the view back and cancel the choice.
        UIView.animateWithDuration(0.16, animations: { () -> Void in
            view.transform = CGAffineTransformIdentity
            view.center = view.superview!.center
        })
        return false;
    }
}

// This is called then a user swipes the view fully left or right.
func view(view: UIView, wasChosenWithDirection: MDCSwipeDirection) -> Void{
    if wasChosenWithDirection == MDCSwipeDirection.Left {
        println("Photo deleted!")
    }else{
        println("Photo saved!")
    }
}

If you're using CocoaPods 0.36+ (perhaps because you want to include pods that contain Swift code) and you've included the use_frameworks! directive in your Podfile, then you've converted all your pods (including MDCSwipeToChoose) into frameworks. Therefore, you'll need to include the line

import MDCSwipeToChoose

...in your Swift files (even if you're using a bridging header).

More Generic Swiping

You don't have to use a subclass of MDCChooseView. You can use the mdc_swipeToChooseSetup: method on any UIView to enable swipe-to-choose.

In the following example, we adjust the opacity of a UIWebView when it's panned left and right.

#import <MDCSwipeToChoose/MDCSwipeToChoose.h>

// ... in a view controller

- (void)viewDidLoad {
    [super viewDidLoad];

    MDCSwipeOptions *options = [MDCSwipeOptions new];
    options.delegate = self;
    options.onPan = ^(MDCPanState *state){
        switch (state.direction) {
            case MDCSwipeDirectionLeft:
                self.webView.alpha = 0.5f - state.thresholdRatio;
                break;
            case MDCSwipeDirectionRight:
                self.webView.alpha = 0.5f + state.thresholdRatio;
                break;
            case MDCSwipeDirectionNone:
                self.webView.alpha = 0.5f;
                break;
        }
    };
    [self.webView mdc_swipeToChooseSetup:options];
}

##Swiping in Swift

The following is an example of how you can use MDCSwipeToChooseView to display a photo in swift. The user can choose to delete it by swiping left, or save it by swiping right.

First you must create a BridgingHeader.h file

#ifndef ProjectName_BridgingHeader_h
#define ProjectName_BridgingHeader_h


#import <UIKit/UIKit.h>
#import <MDCSwipeToChoose/MDCSwipeToChoose.h>

#endif

You must then add the bridging header file to the project by navigating to Build Settings then searching for 'Bridging Header'. Double click the field and type: ProjectName/BridgingHeader.h as the value

// Creating and Customizing a MDCSwipeToChooseView

override func viewDidLoad(){
    super.viewDidLoad()

    // You can customize MDCSwipeToChooseView using MDCSwipeToChooseViewOptions.
    var options:MDCSwipeToChooseViewOptions = MDCSwipeToChooseViewOptions()
    options.delegate = self
    options.likedText = "Keep"
    options.likedColor = UIColor.blueColor()
    options.nopeText = "Delete"
    options.onPan = { state -> Void in
    if (state.thresholdRatio == 1.0 && state.direction == MDCSwipeDirection.Left) {
        println("Let go now to delete the photo!")
    }
}

var view:MDCSwipeToChooseView = MDCSwipeToChooseView(frame:self.view.bounds, options:options)
    view.imageView.image = UIImage(named:"photo")
    self.view.addSubview(view)
}

// MDCSwipeToChooseDelegate Callbacks

// This is called when a user didn't fully swipe left or right.
func viewDidCancelSwipe(view: UIView) -> Void{
    println("Couldn't decide, huh?")
}

// Sent before a choice is made. Cancel the choice by returning `false`. Otherwise return `true`.
func view(view:UIView, shouldBeChosenWithDirection:MDCSwipeDirection) -> Bool {
    if (shouldBeChosenWithDirection == MDCSwipeDirection.Left) {
        return true;
    } else {
        // Snap the view back and cancel the choice.
        UIView.animateWithDuration(0.16, animations: { () -> Void in
            view.transform = CGAffineTransformIdentity
            view.center = self.view.center
        })
    return false;
    }
}

// This is called then a user swipes the view fully left or right.
func view(view: UIView, wasChosenWithDirection: MDCSwipeDirection) -> Void{
    if (wasChosenWithDirection == MDCSwipeDirection.Left) {
        println("Photo deleted!");
    } else {
        println("Photo saved!");
    }
}