NSLayoutConstraint+Init.swift

NSLayoutConstraint+Init.swift

//
//  NSLayoutConstraint+Init.swift
//  Created by Benjamin Wheeler starting 6/2013
//
//

import UIKit

// improves the clarity and flexibility of NSLayoutConstraint
extension NSLayoutConstraint {
    
    convenience init(fromItem: UIView, fromAttribute: NSLayoutAttribute, relatedBy: NSLayoutRelation=NSLayoutRelation.Equal, toItem toItemParam: UIView?=nil, toAttribute toAttributeParam: NSLayoutAttribute?=nil, multiplier: CGFloat=1.0, constant: CGFloat=0.0) {
        var toItemResolved: UIView? = toItemParam
        if toItemResolved == nil {
            toItemResolved = fromItem
        }
        var toAttributeResolved: NSLayoutAttribute? = toAttributeParam
        if toAttributeResolved == nil {
            toAttributeResolved = fromAttribute
        }
        self.init(item: fromItem, attribute: fromAttribute, relatedBy: relatedBy, toItem: toItemResolved!, attribute: toAttributeResolved!, multiplier: multiplier, constant: constant)
    }
    
    class func add(commonAncestor: UIView, fromItem: UIView, fromAttribute: NSLayoutAttribute, relatedBy: NSLayoutRelation=NSLayoutRelation.Equal, toItem toItemParam: UIView?=nil, toAttribute toAttributeParam: NSLayoutAttribute?=nil, multiplier: CGFloat=1.0, constant: CGFloat=0.0) {
        var toItemResolved: UIView? = toItemParam
        if toItemResolved == nil {
            toItemResolved = fromItem
        }
        var toAttributeResolved: NSLayoutAttribute? = toAttributeParam
        if toAttributeResolved == nil {
            toAttributeResolved = fromAttribute
        }
        let constraintToAdd = NSLayoutConstraint(fromItem: fromItem, fromAttribute: fromAttribute, relatedBy: relatedBy, toItem: toItemResolved!, toAttribute: toAttributeResolved!, multiplier: multiplier, constant: constant)
        commonAncestor.addConstraint(constraintToAdd)
    }
    
    class func setEdges(commonAncestor: UIView, fromItem: UIView, toItem: UIView) {
        commonAncestor.addConstraint(NSLayoutConstraint(fromItem: fromItem, fromAttribute: .Top, toItem: toItem))
        commonAncestor.addConstraint(NSLayoutConstraint(fromItem: fromItem, fromAttribute: .Bottom, toItem: toItem))
        commonAncestor.addConstraint(NSLayoutConstraint(fromItem: fromItem, fromAttribute: .Left, toItem: toItem))
        commonAncestor.addConstraint(NSLayoutConstraint(fromItem: fromItem, fromAttribute: .Right, toItem: toItem))
    }
    
    class func setWidth(item: UIView, width: CGFloat) {
        item.addConstraint(NSLayoutConstraint(fromItem: item, fromAttribute: NSLayoutAttribute.Width, constant: width))
    }
    
    class func setHeight(item: UIView, height: CGFloat) {
        item.addConstraint(NSLayoutConstraint(fromItem: item, fromAttribute: NSLayoutAttribute.Height, constant: height))
    }
}

// lets constraints know about their owners, so they can add and remove themselves at will
class Straint {
    var constraint: NSLayoutConstraint
    var commonAncestor: UIView?

    init(commonAncestor: UIView, fromItem: UIView, fromAttribute: NSLayoutAttribute, relatedBy: NSLayoutRelation=NSLayoutRelation.Equal, toItem: UIView?=nil, toAttribute: NSLayoutAttribute?=nil, multiplier: CGFloat=1.0, constant: CGFloat=0.0) {
        
        self.constraint = NSLayoutConstraint(fromItem: fromItem, fromAttribute: fromAttribute, relatedBy: relatedBy, toItem: toItem, toAttribute: toAttribute, multiplier: multiplier, constant: constant)
        self.commonAncestor = commonAncestor
    }

    class func add(commonAncestor: UIView, fromItem: UIView, fromAttribute: NSLayoutAttribute, relatedBy: NSLayoutRelation=NSLayoutRelation.Equal, toItem: UIView?=nil, toAttribute: NSLayoutAttribute?=nil, multiplier: CGFloat=1.0, constant: CGFloat=0.0) {
        let newStraint = Straint(commonAncestor: commonAncestor, fromItem: fromItem, fromAttribute: fromAttribute, relatedBy: relatedBy, toItem: toItem, toAttribute: toAttribute, multiplier: multiplier, constant: constant)
        newStraint.add()
    }
    
    func add() -> Bool {
        if self.commonAncestor != nil {
            self.commonAncestor!.addConstraint(self.constraint)
            return true
        }
        return false
    }
    
    func remove() -> Bool {
        if self.commonAncestor != nil {
            self.commonAncestor!.removeConstraint(self.constraint)
            return true
        }
        return false
    }
}