UITextView - addSubview - Autolayout - ios

Question

Problem:
I have created a subclass of UITextView and added a subview v1.
I am using Autolayout, so I tried to add constraints for positioning the subview v1.
Error:
It throws the following error:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Auto Layout still required after executing -layoutSubviews.
Attempts Made:
I have tried creating the constraints inside layoutSubviews and yet i get the same error
Objective
My main objective is to add a fading effect at the bottom of the text view
Question:
Is there a better way to attain my objective ?
How do I resolve this error ?

Answer 1

Thanks to #mackworth for the suggestion which led to the solution
For completeness I am answering it.
Overview:
There seems to be some trouble adding subview on UITextView and then using Autolayout.
Solution:
So the solution is to create the HazeView as a subview to the parent view of UITextView.
Steps:
Create a UITextView
Create a HazeView (subclass from UIView)
Add both UITextView and HazeView as subview to the same parent view
Position HazeView at the bottom of the UITextView
Ensure that the background colour of HazeView is [UIColor clearColor]
Disable user interaction on HazeView
It is best to create a subclass of UIView and put the UITextView and HazeView inside that so that it can be reusable
Creating HazeView:
self.hazeView.backgroundColor = [UIColor clearColor];
HazeView is a subclass of UIView
- (void)drawRect:(CGRect)rect
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = UIGraphicsGetCurrentContext();
UIColor *color1 = [UIColor colorWithRed:1.0 green:1.0
blue:1.0 alpha:0.25];
UIColor *color2 = [UIColor colorWithRed:1.0 green:1.0
blue:1.0 alpha:0.5];
UIColor *color3 = [UIColor colorWithRed:1.0 green:1.0
blue:1.0 alpha:0.75];
NSArray *gradientColors = #[(id) color1.CGColor,
(id) color2.CGColor,
(id) color3.CGColor];
CGFloat gradientLocations[] = {0, 0.50, 1};
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) gradientColors, gradientLocations);
CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient);
}

Answer 2

I suggest you to use the following library for Autolayout:
https://github.com/jrturton/UIView-Autolayout
It is very easy to add constraints with this.
Create the subclass of UITextView and add the constraints in -(void)didMoveToSuperview
as:
-(void)didMoveToSuperview
{
[self.subview pinToSuperviewEdges:JRTViewPinBottomEdge | JRTViewPinLeftEdge | JRTViewPinRightEdge inset:0];
[self.subview constrainToHeight:10];
}