NSLayoutConstraint builder that allows quick cloning / creation of a constraint.

LayoutConstraintBuilder.swift

//
//  Created by Khanh Le Do on 16/4/16.
//  Copyright © 2016 kloc. All rights reserved.
//

import Foundation
import UIKit

public class LayoutConstraintBuilder {
    
    private var mOrigin: NSLayoutConstraint?
    
    private var mFirstItem: AnyObject?
    private var mSecondItem: AnyObject?
    private var mPriority: UILayoutPriority?
    private var mRelation: NSLayoutRelation?
    private var mMultiplier: CGFloat?
    private var mConstant: CGFloat?
    private var mFirstAttribute: NSLayoutAttribute?
    private var mSecondAttribute: NSLayoutAttribute?
    
    public init() {
        // Nothing to init
    }
    
    public init(origin: NSLayoutConstraint) {
        self.mOrigin = origin
    }
    
    public func setFirstItem(firstItem: AnyObject?) -> LayoutConstraintBuilder {
        self.mFirstItem = firstItem
        return self
    }
    
    public func setSecondItem(secondItem: AnyObject?) -> LayoutConstraintBuilder {
        self.mSecondItem = secondItem
        return self
    }
    
    public func setPriority(priority: UILayoutPriority?) -> LayoutConstraintBuilder {
        self.mPriority = priority
        return self
    }
    
    public func setRelation(relation: NSLayoutRelation?) -> LayoutConstraintBuilder {
        self.mRelation = relation
        return self
    }
    
    public func setMultiplier(multiplier: CGFloat?) -> LayoutConstraintBuilder {
        self.mMultiplier = multiplier
        return self
    }
    
    public func setConstant(constant: CGFloat?) -> LayoutConstraintBuilder {
        self.mConstant = constant
        return self
    }
    
    public func setFirstAttribute(firstAttribute: NSLayoutAttribute?) -> LayoutConstraintBuilder {
        self.mFirstAttribute = firstAttribute
        return self
    }
    
    public func setSecondAttribute(secondAttribute: NSLayoutAttribute?) -> LayoutConstraintBuilder {
        self.mSecondAttribute = secondAttribute
        return self
    }
    
    public func build() -> NSLayoutConstraint {
        let priority = (self.mPriority != nil ? self.mPriority : self.mOrigin?.priority)
        let relation = (self.mRelation != nil ? self.mRelation : self.mOrigin?.relation)
        let multiplier = (self.mMultiplier != nil ? self.mMultiplier : self.mOrigin?.multiplier)
        let constant = (self.mConstant != nil ? self.mConstant : self.mOrigin?.constant)
        let firstAttribute = (self.mFirstAttribute != nil ? self.mFirstAttribute : self.mOrigin?.firstAttribute)
        let secondAttribute = (self.mSecondAttribute != nil ? self.mSecondAttribute : self.mOrigin?.secondAttribute)
        
        let firstItem = (self.mFirstItem != nil ? self.mFirstItem : self.mOrigin?.firstItem)
        let secondItem = (self.mSecondItem != nil ? self.mSecondItem : self.mOrigin?.secondItem)
        
        let ret = NSLayoutConstraint(item: firstItem!, attribute: firstAttribute!, relatedBy: relation!, toItem: secondItem, attribute: secondAttribute!, multiplier: multiplier!, constant: constant!)
        ret.priority = priority!
        return ret
    }
}