iOS - Getting information from the View Controller to drawRect in the View

Question

My question relates to Assignment 3 in CS193p.

Im having a terrible time getting drawRect in my View to receive information passed from my View Controller. Basically, my goal is to pass view-specific information (like self.view.size.width) to the controller, have it make some modifications (like result = self.view.size.width * 2), and pass result back to drawRect so that it could take the new info and draw it. Im pretty sure I have my delegation set up correctly, and really have tried a list of potential work-arounds:

• make a public View @property, which I access in my controller.m via

  View *newView someResult = newView.variable

which I would then try to access from my view.m via

self.variable

• use methods set in my View's @protocal, which I try to pass data via myView.dataSource someMethod:someData

But so far none of these are currently working (i.e. my self.variable would always come out to be 0, which shows that no data was passed to it). Your help much appreciated!

UPDATE:

The culprit was that, in the storyboard, I didn't control-drag the View Controller to the View, and hence the Controller was never connected... but at least now it works. ^_^

Answer 1

View *newView someResult = newView.variable is not valid syntax. If newView.variable is not of type View then that is a problem.

If newView is already declared, you would access variable using int myValue = newView.variable (that is, asuming it is of int type).

An example would be:

// Somewhere in your code, you declare your object
UIView *otherView = [[UIView alloc] init];

// Somewhere else, you set a variable of your object
otherView.backgroundColor = [UIColor blackColor];

// Again, somewhere else you want to access that value
UIColor *thatColor = otherView.backgroundColor;

I hope this explains it well enough.

Answer 2

Is this the correct description of what you want to do? You have a view controller (presumably the calculator type view controller from the course) and you want to communicate between that view controller (whose view has the calculator buttons) and a view other than it's own?

If so, here are the steps you should take:

In your view that you want to receive information from a delegate:

Declare an @protocol with the method you want the delegate to implement. Declare a property in the header file of the view that conforms to the aforementioned delegate: @property (nonatomic, weak) delegate<NameOfTheProtocol> delegate;

In the view controller you want to act as the delegate, declare it conforms to the protocol: MyClass: UIViewController <NameOfTheProtocol>. In the implementation file of that view controller, implement the methods of the protocol. Where ever you create the view that you want to receive information, set it's delegate property to your view controller.

To pass information between them (I have no idea what information you want to pass), your protocol method might be something like: -(CGPoint)pointToDrawAtGivenPosition:(CGPoint)point

In your view that has the delegate property, you could in drawRect do something like:

CGPoint pointToDrawAt = [self.delegate pointToDrawAtGivenPosition:CGPointMake(100, 100)]; //Now draw that point or whatever.

Basically, the view is asking its delegate to make a decision about where to draw something. It passes some information to the delegate, and the delegate responds with the correct position for the view to draw at.