Using self-invoking closures for tricky mutable dictionary values.

README.md

Swift Self-invoking Closures

While working on the iOS Development with Swift book I decided on this code for an example I'm using in the chapter that talks about composing views together. This is a silly little scroll view that displays a user's bio, and is actually used by a ProfileView that contains this and a UserDetailsView.

Explaination

On line 19 I'm creating the setter for the text property that basically is meant to act as a way to apply default attributes to a plain string and assign it to the bio label's attributedText property.

I started making the NSAttributedString and was ready to have to do a bunch of build up crap to build the dictionary first and the paragraph style and such, and then I realised… SELF-INVOKING CLOSURES! I personally feel this is a bit more "Swift-y" and I was actually really impressed with the fact the type system didn't get in the way here, though that's just because of the context really (type is [AnyObject:AnyObject]).

Would love all your thoughts.

UserBioView.swift

//
//  UserBioView.swift
//  Profile
//
//  Created by Jack Watson-Hamblin on 18/01/2015.
//  Copyright (c) 2015 ACME Inc. All rights reserved.
//

import UIKit

class UserBioView: UIScrollView {

    let bio = UILabel(frame: CGRectZero)
    
    var text: NSString {
        get {
            return bio.text!
        }
        set {
            bio.attributedText = NSAttributedString(string: newValue, attributes: [
                NSParagraphStyleAttributeName : ({
                    let paragraphStyle = NSMutableParagraphStyle()
                    
                    paragraphStyle.lineHeightMultiple = 1.5
                    
                    return paragraphStyle
                })()
            ])
        }
    }
    
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        addSubview(bio)
        
        bio.numberOfLines = 0
        bio.font = UIFont(name: "Georgia", size: 14)
    }
    
    override func layoutSubviews() {
        let bioSize = bio.sizeThatFits(frame.size)
        bio.frame = CGRectMake(20, 20, bioSize.width - 40, bioSize.height - 40)
        self.contentSize = CGSizeMake(bio.frame.size.width + 40, bio.frame.size.height + 60)
    }

}