soemarko · March 23, 2017 18:31 · Mar 23, 2017 · Mar 23, 2017
diff --git a/CalculatorViewController.swift b/CalculatorViewController.swift
@@ -2,7 +2,14 @@
 //  Created by Soemarko Ridwan on 3/23/17.
 //  Copyright © 2017 Soemarko Ridwan. All rights reserved.
 //
-
+//  Dependencies: (to simplify the code)
+//  - ActionKit: https://github.com/ActionKit/ActionKit/tree/swift3
+//    For closure style buttons
+//  - AutoLayout Helper: https://github.com/ustwo/autolayout-helper-swift
+//    I was never a fan of interface builder, a lot more across devices.
+//
+//  Photo: https://tmblr.co/ZBVAFy2Js5KA6
+//
 import UIKit
 
 class aViewController: UIViewController, UITextFieldDelegate {

diff --git a/CalculatorViewController.swift b/CalculatorViewController.swift
@@ -0,0 +1,156 @@
+//
+//  Created by Soemarko Ridwan on 3/23/17.
+//  Copyright © 2017 Soemarko Ridwan. All rights reserved.
+//
+
+import UIKit
+
+class aViewController: UIViewController, UITextFieldDelegate {
+
+	var field: UITextField? = nil
+	var operand: String? = ""
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        // Do any additional setup after loading the view.
+		let wrapper = UIView()
+		self.view.addSubview(wrapper)
+
+		wrapper.addTopConstraint(toView: self.view, constant:80.0)
+		wrapper.addLeftConstraint(toView: self.view, constant:10.0)
+		wrapper.addRightConstraint(toView: self.view, constant:-10.0)
+		wrapper.addHeightConstraint(toView: nil, constant: 40.0)
+		wrapper.backgroundColor = UIColor(white: 0.85, alpha: 0.9)
+
+		field = UITextField()
+
+		wrapper.addSubview(field!)
+		field?.fillSuperView(UIEdgeInsetsMake(5, 10, 5, 10))
+
+		field?.keyboardType = .decimalPad
+
+		let toolBar = UIToolbar()
+		toolBar.barStyle = .default
+		toolBar.isTranslucent = true
+
+		let clearButton = UIBarButtonItem(title: "clear") {
+			// clear
+			self.field?.text = ""
+			self.operand = ""
+		}
+		let addButton = UIBarButtonItem(title: "+") {
+			// add
+			if self.operand != "" {
+				let result = self.compute(string: (self.field?.text)!, operand: self.operand!)
+				self.field?.text = String(result)
+			}
+			self.operand = "+"
+			self.field?.text?.append("+")
+		}
+		let subtractButton = UIBarButtonItem(title: "-") {
+			// sub
+			if self.operand != "" {
+				let result = self.compute(string: (self.field?.text)!, operand: self.operand!)
+				self.field?.text = String(result)
+			}
+			self.operand = "-"
+			self.field?.text?.append("-")
+		}
+		let multiplyButton = UIBarButtonItem(title: "*") {
+			// mul
+			if self.operand != "" {
+				let result = self.compute(string: (self.field?.text)!, operand: self.operand!)
+				self.field?.text = String(result)
+			}
+			self.operand = "*"
+			self.field?.text?.append("*")
+		}
+		let divideButton = UIBarButtonItem(title: "/") {
+			// div
+			if self.operand != "" {
+				let result = self.compute(string: (self.field?.text)!, operand: self.operand!)
+				self.field?.text = String(result)
+			}
+			self.operand = "/"
+			self.field?.text?.append("/")
+		}
+		let equalButton = UIBarButtonItem(title: "=") {
+			// equal
+			if self.operand != "" {
+				let result = self.compute(string: (self.field?.text)!, operand: self.operand!)
+				self.field?.text = String(result)
+			}
+			self.operand = ""
+		}
+
+		let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
+		let fixedSpace = UIBarButtonItem(barButtonSystemItem: .fixedSpace, target: nil, action: nil)
+		fixedSpace.width = 20.0
+
+		toolBar.setItems([clearButton, flexSpace, addButton, fixedSpace, subtractButton, fixedSpace, multiplyButton, fixedSpace, divideButton, fixedSpace, equalButton, fixedSpace], animated: false)
+
+
+		toolBar.isUserInteractionEnabled = true
+		toolBar.sizeToFit()
+
+		field?.inputAccessoryView = toolBar
+		field?.delegate = self
+    }
+
+	override func viewDidAppear(_ animated: Bool) {
+		super.viewDidAppear(animated)
+
+		field?.becomeFirstResponder()
+	}
+
+    override func didReceiveMemoryWarning() {
+        super.didReceiveMemoryWarning()
+        // Dispose of any resources that can be recreated.
+    }
+
+	func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
+		let char = string.cString(using: String.Encoding.utf8)!
+		let isBackSpace = strcmp(char, "\\b")
+
+		if isBackSpace == -92 {
+			if  (textField.text?.hasSuffix("+"))! ||
+				(textField.text?.hasSuffix("-"))! ||
+				(textField.text?.hasSuffix("*"))! ||
+				(textField.text?.hasSuffix("/"))! {
+				self.operand = ""
+				print("remove operand")
+			}
+		}
+
+		return true
+	}
+
+	func compute(string: String, operand: String) -> Double {
+		let comps = string.components(separatedBy: operand)
+
+		if comps.count == 0 {
+			return 0
+		}
+		else if comps.count == 1 {
+			return Double(comps[0])!
+		}
+
+		let left = Double(comps[0]) ?? 0.0
+		let right = Double(comps[1]) ?? 0.0
+
+		switch operand {
+		case "+":
+			return left + right
+		case "-":
+			return left - right
+		case "*":
+			return left * right
+		case "/":
+			return left / right
+		default:
+			return 0
+		}
+	}
+
+}