#pragma mark in Swift?

Question

In Objective C, I can use #pragma mark to mark sections of my code in the symbol navigator. Since this is a C preprocessor command, it's not available in Swift. Is there a stand-in for this in Swift, or do I have to use ugly comments?

Answer 1

You can use // MARK:

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There has also been discussion that liberal use of class extensions might be a better practice anyway. Since extensions can implement protocols, you can e.g. put all of your table view delegate methods in an extension and group your code at a more semantic level than #pragma mark is capable of.

Answer 2

Up to Xcode 5 the preprocessor directive #pragma mark existed.

From Xcode 6 on, you have to use // MARK:

These preprocessor features allow to bring some structure to the function drop down box of the source code editor.

some examples :

// MARK:

-> will be preceded by a horizontal divider

// MARK: your text goes here

-> puts 'your text goes here' in bold in the drop down list

// MARK: - your text goes here

-> puts 'your text goes here' in bold in the drop down list, preceded by a horizontal divider

update : added screenshot 'cause some people still seem to have issues with this :

Answer 3

For those who are interested in using extensions vs pragma marks (as mentioned in the first comment), here is how to implement it from a Swift Engineer:

import UIKit

class SwiftTableViewController: UITableViewController {

    init(coder aDecoder: NSCoder!) {
        super.init(coder: aDecoder)

    }

    override func viewDidLoad() {
        super.viewDidLoad()

    }
}

extension SwiftTableViewController {
    override func numberOfSectionsInTableView(tableView: UITableView?) -> Int {
        return 1
    }

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        return 5
    }

    override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
        let cell = tableView?.dequeueReusableCellWithIdentifier("myCell", forIndexPath: indexPath) as UITableViewCell;

        cell.textLabel.text = "Hello World"

        return cell
    }

}

It's also not necessarily the best practice, but this is how you do it if you like.

Answer 4

Pragma mark - [SOME TEXT HERE] was used in Objective-C to group several function together by line separating.

In Swift you can achieve this using MARK, TODO OR FIXME

i. MARK : //MARK: viewDidLoad

This will create a horizontal line with functions grouped under viewDidLoad(shown in screenshot 1)

ii. TODO : //TODO: - viewDidLoad

This will group function under TODO: - viewDidLoad category (shown in screenshot 2)

iii. FIXME : //FIXME - viewDidLoad

This will group function under FIXME: - viewDidLoad category (shown in screenshot 3)

Check this apple documentation for details.

Answer 5

Xcode Official Doc

Apple's official document about Xcode Jump Bar: Add code annotations to the jump bar and minimap introduces these three:

• TODO:
• FIXME:
• MARK:

There are two more (though not in the doc):

• !!!:
• ???:

which are not supported by some Xcode versions (such as v10.0), but are supported by latest version (v13.3.1).

Screenshots for Sample Versions of Xcode

Example 1 - Xcode 10.1 + macOS 10.14.3 (Mojave)

Example 2 - Xcode 10.0 + macOS 10.13.4 (High Sierra)

Answer 6

In Objective-C code Xcode detects comments like // MARK: - foo which is a bit more portable than #pragma. But these do not seem to be picked up, too (yet?).

Edit: Fixed in Xcode 6 beta 4.

Answer 7

Xcode 8 now handles it as followed and shows up like this in the method dropdown:

Answer 8

I think Extensions is a better way instead of #pragma mark.

The Code before using Extensions:

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    ...

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        ...
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        ...
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        ...
    }
}

The code after using Extensions:

class ViewController: UIViewController {
    ...
}

extension ViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        ...
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        ...
    }
}

extension ViewController: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
       ...
    }
}

Answer 9

Confirmed with an Apple Engineer in the Swift lab this morning at WWDC that there currently aren't any #pragma or equivalent at the moment, they consider this a bug, and it will arrive soon, so I am guessing beta 2, I hope.

Anyway, it's on it's way.

---

Xcode now supports //MARK:, //TODO: and //FIXME landmarks to annotate your code and lists them in the jump bar

Answer 10

There are Three options to add #pragma_mark in Swift:

1) // MARK: - your text here -

2) // TODO: - your text here -

3) // FIXME: - your text here -

Note: Uses - for add separators

Answer 11

Use

// MARK: SectionName

or

// MARK: - SectionName

This will give a line above pragma mark, making it more readable.

For ease just add

// MARK: - <#label#>

to your code snippets.

Alternate way -

Use it in this way

private typealias SectionName = ViewController
private extension SectionName  {
    // Your methods
}

This will not only add mark(just like pragma mark) but also segregate the code nicely.

Answer 12

//# MARK: - Spinner Class Methods

Add a line between the colon and your description to insert a separator line. This helps to organize your code even more. The code and screenshot above make use of the MARK comment with a line included.

1. //# MARK: – Text Methods (LINE)
2. //# MARK: Text Methods (NO LINE)

This only works with the MARK comment.

Answer 13

Professional programer must be use this tag for good code. It is also good for team work.

// MARK: example Web Service start here
// TODO: example 1
// FIXME: Please change BASE url before live 

It is easy to find method like this

Answer 14

In Xcode 11 they added minimap which can be activated Editor -> Minimap.

Minimap will show each mark text for fast orientation in code. Each mark is written like // MARK: Variables

Answer 15

You may also be interested in Swift 4.2 / XCode 10 compiler directives like

#warning("Some string to display")

and

#error("Some error to display")

It might be useful when you really don't want to miss something.