An easing category on CAMediaTimingFunction, with thanks to Mozilla

CAMediaTimingFunction+GMTimingBlock.h

//
//  CAMediaTimingFunction+GMTimingBlock.h
//
//  Created by George MacKerron on 2015/06/11.
//  Copyright (c) 2015 George MacKerron. All rights reserved.
//

#import <QuartzCore/QuartzCore.h>


typedef CGFloat (^GMTimingBlock)(CGFloat);


@interface CAMediaTimingFunction (GMTimingBlock)

- (GMTimingBlock)gm_timingBlock;

@end

CAMediaTimingFunction+GMTimingBlock.mm

//
//  CAMediaTimingFunction+GMTimingBlock.mm
//
//  Created by George MacKerron on 2015/06/11.
//  Copyright (c) 2015 George MacKerron. All rights reserved.
//

#import "CAMediaTimingFunction+GMEasingBlock.h"
#import "nsSMILKeySpline.h"


@implementation CAMediaTimingFunction (GMTimingBlock)

- (GMTimingBlock)gm_timingBlock {
  float coords[4];
  [self getControlPointAtIndex:1 values:coords];
  [self getControlPointAtIndex:2 values:coords + 2];
  nsSMILKeySpline* ks = new nsSMILKeySpline(coords[0], coords[1], coords[2], coords[3]);
  return ^(CGFloat x) {
    return ks->GetSplineValue(x);
  };
}

@end

Example usage

Add these source files to your project:

    https://dxr.mozilla.org/mozilla-central/source/dom/smil/nsSMILKeySpline.h
    https://dxr.mozilla.org/mozilla-central/source/dom/smil/nsSMILKeySpline.mm

Comment out two includes in nsSMILKeySpline.h, which appear to be unused:

    // #include "mozilla/ArrayUtils.h"
    // #include "mozilla/PodOperations.h"

Then use like this:
    
    #import "CAMediaTimingFunction+GMTimingBlock.h"
    
    // ...
    
    GMTimingBlock ease = [[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut] gm_timingBlock];
    NSLog(@"%f, %f, %f, %f, %f, %f", ease(0.0f), ease(0.2f), ease(0.4f), ease(0.6f), ease(0.8f), ease(1.0f));