Delegates vs. events in Cocoa

Posted by aaronstacy on Stack Overflow See other posts from Stack Overflow or by aaronstacy
Published on 2011-11-24T22:19:10Z Indexed on 2011/11/25 1:50 UTC
Read the original article Hit count: 192

Filed under:

objective-c

|

cocoa

I'm writing my first iPhone app, and I've been exploring the design patterns in Cocoa and Objective-C. I come from a background of client-side web development, so I'm trying to wrap my head around delegates.

Specifically, I don't see why delegate objects are needed instead of event handlers. For instance, when the user presses a button, it is handled with an event (UITouchUpInside), but when the user finishes inputting to a text box and closes it with the 'Done' button, the action is handled by calling a method on the text box's delegate (textFieldShouldReturn).

Why use a delegate method instead of an event? I also notice this in the view controller with the viewDidLoad method. Why not just use events?

© Stack Overflow or respective owner

Related posts about objective-c

Blocking access to websites with objective-C / root privileges in objective-C

as seen on Stack Overflow - Search for 'Stack Overflow'
I am writing a program in Objective-C (XCode 3.2, on Snow Leopard) that is capable of either selectively blocking certain sites for a duration or only allow certain sites (and thus block all others) for a duration. The reasoning behind this program is rather simple. I tend to get distracted when I… >>> More
Objective-C with some Objective-C++, calling a normal c++ method "referenced from" problem

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I made an Objective-C project for the iPhone. I had only one cpp class, the soundEngine taken from some Apple demo. Now I'm trying to merge OpenFeint which is coded in Objective-C++. As soon as I drop in the code without even referring to it from my code, when I hit Build, my Objective-C code… >>> More
Add an objective @property attribute in objective-c

as seen on Stack Overflow - Search for 'Stack Overflow'
Does anyone know of a way to add additional attribute types to the @property keyword without modifying the compiler? Or can anyone think of another way to genericize getter/setter creation? Basically, I have a lot of cases in a recent project where it's handy for objects to lazily instantiate their… >>> More
ObjectiveC Syntax for Specifying Protocol Name in Method Argument

as seen on Stack Overflow - Search for 'Stack Overflow'
What's the ObjectiveC syntax for specifying a protocol as an argument in a method? Say I have 2 protocols, MyProtocol and MyProtocolCB: @protocol MyProtocolCB <NSObject> - (void) func; @end @protocol MyProtocol <NSObject> - (void) register:(MyProtocolCB*) cb; @end I'm receiving this… >>> More
ObjectiveC builtin template system ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I am developing an iPhone application and I use HTML to display formatted text. I often display the same webpage, but with a different content. I would like to use a template HTML file, and then fill it with my diffent values. I wonder if ObjectiveC has a template system similar to ERB in Ruby. That… >>> More

Related posts about cocoa

MVC - Cocoa interface - Cocoa Design pattern book

as seen on Stack Overflow - Search for 'Stack Overflow'
So I started reading this book: http://www.amazon.com/Cocoa-Design-Patterns-Erik-Buck/dp/0321535022 On chapter 2 it explains about the MVC design pattern and gives and example which I need some clarification to. The simple example shows a view with the following fields: hourlyRate, WorkHours, Standarthours… >>> More
Drag String data from My Cocoa App to Third-Party Cocoa App

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, I want to drag a row from my tableview and drop it into any other NSTextField in Mac OS X 10.6, and have a string of text be dropped. Drag and drop already works within my app (between a NSTableView and an NSBrowser), but I have had no success putting any data on the pasteboard that can… >>> More
Cocoa equivalent of the Carbon method getPtrSize

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to translate the a carbon method into cocoa into and I am having trouble finding any documentation about what the carbon method getPtrSize really does. From the code I am translating it seems that it returns the byte representation of an image but that doesn't really match up with the name… >>> More
String formatting in cocoa

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi I am trying to send some text in an email from my cocoa app (by using Mail.app). Initially I tried using HTML to send properly formatted text. But the mailto: URL does not support html tags (even after setting headers) So I decided to use formatted string (left-aligning of string) This is what… >>> More
Anyone know the state of cocoa#?

as seen on Stack Overflow - Search for 'Stack Overflow'
Having just updated Mono to 2.6.3 (on OS X), I noticed in the installer that cocoa# 0.9.5 is also installed. However using MonoDevelop there are no cocoa# project templates by default, and I was wondering if anyone knew more about creating cocoa# apps. If you goto the cocoa# page on the Mono site… >>> More