Making a numeric/pin pad with NSLayoutConstraints

NSLayoutConstraints are awesome. But like many cocoa technologies (strangely, all the ones that I like) the learning curve is fairly steep.

The goals was simple, I wanted to make a Numeric pin pad that would center itself in it's container view, while ensuring that all the buttons remained square, and aligned .... Ok, maybe not so simple.

Personally I hate resorting to changing the constraint priority, as I feel that most of the time it's a sign that your approaching the problem incorrectly. You can see a gist of the constraints below, ultimately I found the trick was this gem "-(>=1)-". By placing this between the outermost views and then pinning these to the superview, they provide the layout with the flexibility to meet all of it's requirements without having to adjust the superview or simply "explode".

Lastly, if your wondering why i've adopted this strange grouping mechanism inside my loop, I wanted the subview index have a 1-1 mapping with the button number, with out having to resort to setting tags. This way in the button handers I can look up the index of the sender in the subview collection, and know which button it is.

Like 99% of cocoa code, it's not concise. Disfrutarlo!

Making UIImages with blocks

So i was going to post about something completely different today, but as i was typing i looked at my code, and thought it was verbose and a little bit ugly.

So i made it awesome, and as everyone knows to make your code awesome you add some blocks to it.

My problem was simple, i was faced with the need to create two CGBitmapContext, for the uniformed the following code is required to prepare a bitmap context for drawing.


So after a bit of thought, i decided what i really wanted was a method that did all of this for me, and meant that i didn't have to worry about constantly checking the code for leaks (DRY), and that was pleasant to look at and i came up with the above. The block that you pass in is given a fully formed CGBitmapContext, and the method returns a UIImage generated from that context. Almost like a UIView/CALayer.



So now your thinking, "Yeah, thats cool, but why the [INSERT FOUR LETTER WORD] would i want to use it ?" Well young grasshopper, have you ever wanted to mask a image in code? You know to do those trendy rounded corners ... well yes you can use CALayer's however the idea of using those off the main thread makes me uneasy, and we all know the cool kids do things in the background.


The above actually creates a rounded rect on the fly, and masks the image with it. It's made to be used in a category on UIImage. But look closer, yep thats right kids, no boiler plate, ZERO, NADA, 另, SQUAT (i think you get the point)!

I should take a moment to mention that the awesome code for the rounded rect comes from the awesome Oliver Drobnik, i have the utmost respect for this guy, not just for this snippet, but if you've ever seen his Rich text label and it's associated projects, you'll understand why real soon.