Question

In the introduction to iOS Programming: the Big Nerd Ranch Guide, the authors say that they always create view controllers programmatically, and that instantiating view controllers in Xib files leads to projects that are difficult to comprehend and debug.

What, specifically, makes this problematic? And which difficulties would you encounter?

Are there any specific examples, and how does creating the view controllers in code avoid these problems?

Answer 1

The quote is at Introduction > Style:

We will always create view controllers programmatically. Some
programmers will instantiate view controllers inside XIB file. We’ve
found this practice leads to projects that are difficult to comprehend
and debug.

They talk about instantiation. If you have two view controllers A,B, you can alloc/init B in A’s implementation, or you can drop a reference to B in A’s XIB. In both cases, B may be defined in a XIB or not (the Big Ranch book advises to use XIBs for complex view controllers btw).

---

Anyway, here is the difference:

CitySelectionVC *citySel = [[[CitySelectionVC alloc] initWithCities:self.cities] autorelease];
[self.navigationController pushViewController:citySel animated:TRUE];

vs

citySel.cities = self.cities;
[self.navigationController pushViewController:citySel animated:TRUE];

First case is a explicit instantiation in code. It tells me:

• The VC is created now.
• It needs the cities to work.

The code in the second block references an outlet instantiated in the XIB. It tells me:

• A VC was instantiated at unknown time, with unknown requirements.
• I’m passing the cities.

I favor the first style because it is more explicit, and gives me control of the lifespan of the object.

In iOS 5 you can use Storyboards to create transitions and pass information between controllers. See Session 309 of WWDC2011.