README.md

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.

#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.delegate = self;
    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 = self.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];

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];
}

License

All the source code is distributed under the MIT license. See the LICENSE file for details. The license does not apply to the images used in the sample apps.