CODEWITHSUNDEEP
iosswift
Sherekan
Sherekan

Reputation: 536

Why do all methods have the same name in delegate?

i'm starting with Swift by developing a simple application with a tableView, a request to a server and a few things more. I realized that every method inside UITableViewDelegate protocol is named in the same way (i guess it might be the same with other protocols) and the differences are made by changing the parameters passed to those methods (which are called "tableView" by the way).

I was wondering why Apple would do something like this, as it's a bit messy when i try to implement method from this protocol, as i can't start typing "didSele..." just to autocomplete with "didSelectRowAtIndexPath"; instead i have to type "tableView" to get a list of all available methods and manually search for the one whose second parameter is "didSelectRowAtIndexPath".

Everything's working fine, but just trying to know WHY could this be done this way.

Thank you so much in advice :)

PS: There's a screenshot about what i'm saying:

Image showing a list of "tableView" functions with different parameters names

Upvotes: 3

Views: 926

Answers (3)

DarkDust
DarkDust

Reputation: 92384

Swift is designed to be compatible with Objective-C. After all, almost all existing OS X and iOS APIs are in Objective-C and C (with a bit of C++ code here and there). Swift needs to be able to use those APIs and thus support most Objective-C features one way or the other. One of the most important features of Objective-C is how method calls are made.

For example, in C, a function with 3 arguments is called like this:

foo(1, "bar", 3);

You don't know what the arguments are supposed to be. So in Objective-C, the arguments are interleaved with the method name. For example, a method's name might be fooWithNumber:someString:anotherNumber: and it would be called like:

[anObject fooWithNumber:1 someString:@"bar" anotherNumber:3];

Swift now tries to be compatible with this Objective-C feature. It thus supports a form of named arguments. The call in Swift would look like:

anObject.foo(number:1, someString:@"bar", anotherNumber:3)

Often Swift method definitions are written so that you don't need to explicitly name the first argument, like:

anObject.foo(1, someString:@"bar", anotherNumber:3)

If you look up the UITableViewDelegate protocol documentation and select Objective-C you can see that all of these methods start with tableView: to designate the sender, but from then on they are very different. The list you've cited is the result of the conversion from Objective-C to Swift naming convention.

Upvotes: 2

fluidsonic
fluidsonic

Reputation: 4676

The method name is not only the first word but also the public names of the parameters.

E.g. it the method name is not tableView() but tableView(_:didSelectRowAtIndexPath:).

Upvotes: 1

BoilingLime
BoilingLime

Reputation: 2267

It is just naming conventions. It is the same in Objective-C. You can have a look to this page. Without these conventions it would be a complete mess.

Upvotes: 1

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