If you design your data model with parent entity, then you are most likely doing it wrong, unknowingly.

Because when you do so, Core Data will create 1 common table for ALL the children entities!

This is bad design (on Core Data part) and it will slow down the performance.

Read more about this under the section Entity Hierarchy vs. Class Hierarchy.

If you have been using MoPub to serve your banner ads eg. for backfills, it is important that you know it is possible to serve retina sizes @2x.

This means you can upload 640x100 instead of 320x50.

MoPub documentation has been poor to highlight this capability. It is found only in their forum.

A common UI design pattern is to make an image fill the header as you scroll beyond the top, like this:

This post will show you how to do that, easily.

It is a very common task in iOS when you have eg UITextField, which on tap brings up the keyboard, and in the process obscure part of your view.

Unfortuantely, iOS leaves this situation to the developer to handle.

If you have a simple form for users to enter some text, then I suggest using IQKeyboardManager to this common problem.

It is good practise to generate documentation for your project.

appledoc is a tool to help generating the HTML docs from your code.

This is a guide on how to do it.

Unwind segue is a very nice concept in iOS to “go back” to a previous view controller.

There is an Apple Guide to using it, and a good in a nutshell about it.

Here, I will share how I use it in real world applications.

PromiseKit is a wonderful library for dealing for async callbacks.

Other similar libraries are Bolts Framework and ReactiveCocoa, but personally I felt the syntax and design of PromiseKit to be much better.

Initially, I wanted to write a guide on some common usage of PromiseKit, but I find that the common recipes by Phil Mitchell himself is great.

Therefore, I will be emphasizing only on some usage/pitfall.

The Content view in a UIScrollView is very unique when it comes to configuring a scroll view with auto layout.

In short, the constraints needed:

1. You must have only 1 child view in UIScrollView, which we refered to as Content view

2. Content is usually pinned up, down, left and right to the UIScrollView

3. In addition, Content must define it’s width and height, which is the scrollable area. In most case you will have the width equal to the UIScrollView. The height is set to 888 in example below, but usually you will have the views within in to determine the overall height.

Customizing UINavigationBar remains a not-easy-to-remember topic.

When I need to change the looks of the nav bar – such as changing the Back arrow, or title, or making it transparent – I always need to google for the code.

Encountered the same bug when creating a UIScreenEdgePanGestureRecognizer via Interface Builder.

It just didn’t work as expected: the selector is never called.

Other gesture recognizers work. Except panning from edge.