Create UIView+MDCSwipeToChoose.m

UIView+MDCSwipeToChoose.m

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+//
+// UIView+MDCSwipeToChoose.m
+//
+// Copyright (c) 2014 to present, Brian Gesiak @modocache
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+
+#import "UIView+MDCSwipeToChoose.h"
+#import "MDCSwipeToChoose.h"
+#import "MDCViewState.h"
+#import "MDCGeometry.h"
+#import <objc/runtime.h>
+
+const void * const MDCSwipeOptionsKey = &MDCSwipeOptionsKey;
+const void * const MDCViewStateKey = &MDCViewStateKey;
+
+@implementation UIView (MDCSwipeToChoose)
+
+#pragma mark - Public Interface
+
+- (void)mdc_swipeToChooseSetup:(MDCSwipeOptions *)options {
+    self.mdc_options = options ? options : [MDCSwipeOptions new];
+    self.mdc_viewState = [MDCViewState new];
+    self.mdc_viewState.originalCenter = self.center;
+
+    [self mdc_setupPanGestureRecognizer];
+}
+
+- (void)mdc_swipe:(MDCSwipeDirection)direction {
+    [self mdc_swipeToChooseSetupIfNecessary];
+
+    // A swipe in no particular direction "finalizes" the swipe.
+    if (direction == MDCSwipeDirectionNone) {
+        [self mdc_finalizePosition];
+        return;
+    }
+
+    // Moves the view to the minimum point exceeding the threshold.
+    // Transforms and executes pan callbacks as well.
+    void (^animations)(void) = ^{
+        CGPoint translation = [self mdc_translationExceedingThreshold:self.mdc_options.threshold
+                                                            direction:direction];
+        self.center = MDCCGPointAdd(self.center, translation);
+        [self mdc_rotateForTranslation:translation
+                     rotationDirection:MDCRotationAwayFromCenter];
+        [self mdc_executeOnPanBlockForTranslation:translation];
+    };
+
+    // Finalize upon completion of the animations.
+    void (^completion)(BOOL) = ^(BOOL finished) {
+        if (finished) { [self mdc_finalizePosition]; }
+    };
+
+    [UIView animateWithDuration:self.mdc_options.swipeAnimationDuration
+                          delay:0.0
+                        options:self.mdc_options.swipeAnimationOptions
+                     animations:animations
+                     completion:completion];
+}
+
+#pragma mark - Internal Methods
+
+- (void)setMdc_options:(MDCSwipeOptions *)options {
+    objc_setAssociatedObject(self, MDCSwipeOptionsKey, options, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (MDCSwipeOptions *)mdc_options {
+    return objc_getAssociatedObject(self, MDCSwipeOptionsKey);
+}
+
+- (void)setMdc_viewState:(MDCViewState *)state {
+    objc_setAssociatedObject(self, MDCViewStateKey, state, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (MDCViewState *)mdc_viewState {
+    return objc_getAssociatedObject(self, MDCViewStateKey);
+}
+
+#pragma mark Setup
+
+- (void)mdc_swipeToChooseSetupIfNecessary {
+    if (!self.mdc_options || !self.mdc_viewState) {
+        [self mdc_swipeToChooseSetup:nil];
+    }
+}
+
+- (void)mdc_setupPanGestureRecognizer {
+    SEL action = @selector(mdc_onSwipeToChoosePanGestureRecognizer:);
+    UIPanGestureRecognizer *panGestureRecognizer =
+    [[UIPanGestureRecognizer alloc] initWithTarget:self
+                                            action:action];
+    [self addGestureRecognizer:panGestureRecognizer];
+}
+
+#pragma mark Translation
+
+- (void)mdc_finalizePosition {
+    MDCSwipeDirection direction = [self mdc_directionOfExceededThreshold];
+    switch (direction) {
+        case MDCSwipeDirectionRight:
+        case MDCSwipeDirectionLeft: {
+            CGPoint translation = MDCCGPointSubtract(self.center,
+                                                     self.mdc_viewState.originalCenter);
+            [self mdc_exitSuperviewFromTranslation:translation];
+            break;
+        }
+        case MDCSwipeDirectionNone:
+            [self mdc_returnToOriginalCenter];
+            [self mdc_executeOnPanBlockForTranslation:CGPointZero];
+            break;
+    }
+}
+
+- (void)mdc_returnToOriginalCenter {
+    [UIView animateWithDuration:self.mdc_options.swipeCancelledAnimationDuration
+                          delay:0.0
+                        options:self.mdc_options.swipeCancelledAnimationOptions
+                     animations:^{
+                         self.transform = CGAffineTransformIdentity;
+                         self.center = self.mdc_viewState.originalCenter;
+                     } completion:^(BOOL finished) {
+                         id<MDCSwipeToChooseDelegate> delegate = self.mdc_options.delegate;
+                         if ([delegate respondsToSelector:@selector(viewDidCancelSwipe:)]) {
+                             [delegate viewDidCancelSwipe:self];
+                         }
+                     }];
+}
+
+- (void)mdc_exitSuperviewFromTranslation:(CGPoint)translation {
+    MDCSwipeDirection direction = [self mdc_directionOfExceededThreshold];
+    id<MDCSwipeToChooseDelegate> delegate = self.mdc_options.delegate;
+    if ([delegate respondsToSelector:@selector(view:shouldBeChosenWithDirection:)]) {
+        BOOL should = [delegate view:self shouldBeChosenWithDirection:direction];
+        if (!should) {
+            return;
+        }
+    }
+
+    MDCSwipeResult *state = [MDCSwipeResult new];
+    state.view = self;
+    state.translation = translation;
+    state.direction = direction;
+    state.onCompletion = ^{
+        if ([delegate respondsToSelector:@selector(view:wasChosenWithDirection:)]) {
+            [delegate view:self wasChosenWithDirection:direction];
+        }
+    };
+    self.mdc_options.onChosen(state);
+}
+
+- (void)mdc_executeOnPanBlockForTranslation:(CGPoint)translation {
+    if (self.mdc_options.onPan) {
+        CGFloat thresholdRatio = MIN(1.f, fabsf(translation.x)/self.mdc_options.threshold);
+
+        MDCSwipeDirection direction = MDCSwipeDirectionNone;
+        if (translation.x > 0.f) {
+            direction = MDCSwipeDirectionRight;
+        } else if (translation.x < 0.f) {
+            direction = MDCSwipeDirectionLeft;
+        }
+
+        MDCPanState *state = [MDCPanState new];
+        state.view = self;
+        state.direction = direction;
+        state.thresholdRatio = thresholdRatio;
+        self.mdc_options.onPan(state);
+    }
+}
+
+#pragma mark Rotation
+
+- (void)mdc_rotateForTranslation:(CGPoint)translation
+               rotationDirection:(MDCRotationDirection)rotationDirection {
+    CGFloat rotation = MDCDegreesToRadians(translation.x/100 * self.mdc_options.rotationFactor);
+    self.transform = CGAffineTransformRotate(CGAffineTransformIdentity,
+                                             rotationDirection * rotation);
+}
+
+#pragma mark Threshold
+
+- (CGPoint)mdc_translationExceedingThreshold:(CGFloat)threshold
+                                   direction:(MDCSwipeDirection)direction {
+    NSParameterAssert(direction != MDCSwipeDirectionNone);
+
+    CGFloat offset = threshold + 1.f;
+    switch (direction) {
+        case MDCSwipeDirectionLeft:
+            return CGPointMake(-offset, 0);
+        case MDCSwipeDirectionRight:
+            return CGPointMake(offset, 0);
+        default:
+            [NSException raise:NSInternalInconsistencyException
+                        format:@"Invallid direction argument."];
+            return CGPointZero;
+    }
+}
+
+- (MDCSwipeDirection)mdc_directionOfExceededThreshold {
+    if (self.center.x > self.mdc_viewState.originalCenter.x + self.mdc_options.threshold) {
+        return MDCSwipeDirectionRight;
+    } else if (self.center.x < self.mdc_viewState.originalCenter.x - self.mdc_options.threshold) {
+        return MDCSwipeDirectionLeft;
+    } else {
+        return MDCSwipeDirectionNone;
+    }
+}
+
+#pragma mark Gesture Recognizer Events
+
+- (void)mdc_onSwipeToChoosePanGestureRecognizer:(UIPanGestureRecognizer *)panGestureRecognizer {
+    UIView *view = panGestureRecognizer.view;
+
+    if (panGestureRecognizer.state == UIGestureRecognizerStateBegan) {
+        self.mdc_viewState.originalCenter = view.center;
+
+        // If the pan gesture originated at the top half of the view, rotate the view
+        // away from the center. Otherwise, rotate towards the center.
+        if ([panGestureRecognizer locationInView:view].y < view.center.y) {
+            self.mdc_viewState.rotationDirection = MDCRotationAwayFromCenter;
+        } else {
+            self.mdc_viewState.rotationDirection = MDCRotationTowardsCenter;
+        }
+    } else if (panGestureRecognizer.state == UIGestureRecognizerStateEnded) {
+        // Either move the view back to its original position or move it off screen.
+        [self mdc_finalizePosition];
+    } else {
+        // Update the position and transform. Then, notify any listeners of
+        // the updates via the pan block.
+        CGPoint translation = [panGestureRecognizer translationInView:view];
+        view.center = MDCCGPointAdd(self.mdc_viewState.originalCenter, translation);
+        [self mdc_rotateForTranslation:translation
+                     rotationDirection:self.mdc_viewState.rotationDirection];
+        [self mdc_executeOnPanBlockForTranslation:translation];
+    }
+}
+
+@end