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@nicklockwood
nicklockwood / Hacking UIView Animation Blocks.md
Last active Oct 16, 2019
This article was originally written for objc.io issue 12, but didn't make the cut. It was intended to be read in the context of the other articles, so if you aren't familiar with concepts such as CALayer property animations and the role of actionForKey:, read the articles in that issue first.
View Hacking UIView Animation Blocks.md

Hacking UIView animation blocks for fun and profit

In this article, I'm going to explore a way that we can create views that implement custom Core Animation property animations in a natural way.

As we know, layers in iOS come in two flavours: Backing layers and hosted layers. The only difference between them is that the view acts as the layer delegate for its backing layer, but not for any hosted sublayers.

In order to implement the UIView transactional animation blocks, UIView disables all animations by default and then re-enables them individually as required. It does this using the actionForLayer:forKey: method.

Somewhat strangely, UIView doesn't enable animations for every property that CALayer does by default. A notable example is the layer.contents property, which is animatable by default for a hosted layer, but cannot be animated using a UIView animation block.

View gist:b0c00a889dc2a17efad9
var randomNumbers = [42, 12, 88, 62, 63, 56, 1, 77, 88, 97, 97, 20, 45, 91, 62, 2, 15, 31, 59, 5]
func partition(v: Int[], left: Int, right: Int) -> Int {
var i = left
for j in (left + 1)..(right + 1) {
if v[j] < v[left] {
i += 1
(v[i], v[j]) = (v[j], v[i])
}
}
@raven
raven / Breakpoints_v2.xcbkptlist
Last active Aug 30, 2019
Symbolic breakpoint for dynamically linking libReveal against UIApplicationMain
View Breakpoints_v2.xcbkptlist
<?xml version="1.0" encoding="UTF-8"?>
<Bucket
type = "2"
version = "2.0">
<Breakpoints>
<BreakpointProxy
BreakpointExtensionID = "Xcode.Breakpoint.SymbolicBreakpoint">
<BreakpointContent
shouldBeEnabled = "Yes"
ignoreCount = "0"
@bomberstudios
bomberstudios / sketch-plugins.md
Last active Feb 13, 2019
A list of Sketch plugins hosted at GitHub, in no particular order.
View sketch-plugins.md
@mayoff
mayoff / drawArc.m
Created Apr 7, 2013
Use Core Graphics to draw an arc with a gradient fill, a stroked outline, and a shadow. http://stackoverflow.com/questions/15866179/draw-segments-from-a-circle-or-donut
View drawArc.m
static UIImage *imageWithSize(CGSize size) {
static CGFloat const kThickness = 20;
static CGFloat const kLineWidth = 1;
static CGFloat const kShadowWidth = 8;
UIGraphicsBeginImageContextWithOptions(size, NO, 0); {
CGContextRef gc = UIGraphicsGetCurrentContext();
CGContextAddArc(gc, size.width / 2, size.height / 2,
(size.width - kThickness - kLineWidth) / 2,
-M_PI / 4, -3 * M_PI / 4, YES);
@kylestew
kylestew / NSObject+PWObject.c
Created Feb 24, 2012
Category - Perform Block After Delay
View NSObject+PWObject.c
#import "NSObject+PWObject.h"
@implementation NSObject (PWObject)
- (void)performBlock:(void (^)(void))block afterDelay:(NSTimeInterval)delay {
int64_t delta = (int64_t)(1.0e9 * delay);
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, delta), dispatch_get_main_queue(), block);
}
@end
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