計算乘除的結果

AndroidCalculator/Calculator.swift

@@ -20,7 +20,51 @@ class Calculator {
       return result
     }
   }
-  var result = ""
+  
+  var result: String {
+    get {
+      if formula.count < 3 {
+        return ""
+      }
+      
+      var calculatingFormula = formula
+      if ["+", "-", "×", "÷"].firstIndex(of: calculatingFormula.last!) != nil {
+        calculatingFormula.removeLast()
+      }
+      
+      while true {
+        let indexOfMultiplication = calculatingFormula.firstIndex(of: "×")
+        let indexOfDivision = calculatingFormula.firstIndex(of: "÷")
+        
+        if indexOfMultiplication == nil && indexOfDivision == nil {
+          break
+        }
+        if indexOfMultiplication != nil {
+          if indexOfDivision == nil || indexOfMultiplication! < indexOfDivision! {
+            let number1 = Double(calculatingFormula[indexOfMultiplication! - 1])!
+            let number2 = Double(calculatingFormula[indexOfMultiplication! + 1])!
+            calculatingFormula[indexOfMultiplication! - 1] = String(number1 * number2)
+            calculatingFormula.remove(at: indexOfMultiplication! + 1)
+            calculatingFormula.remove(at: indexOfMultiplication!)
+            continue
+          }
+        }
+        if indexOfDivision != nil {
+          if indexOfMultiplication == nil || indexOfDivision! < indexOfMultiplication! {
+            let number1 = Double(calculatingFormula[indexOfDivision! - 1])!
+            let number2 = Double(calculatingFormula[indexOfDivision! + 1])!
+            calculatingFormula[indexOfDivision! - 1] = String(number1 / number2)
+            calculatingFormula.remove(at: indexOfDivision! + 1)
+            calculatingFormula.remove(at: indexOfDivision!)
+            continue
+          }
+        }
+      }
+      
+      print(calculatingFormula)
+      return calculatingFormula[0]
+    }
+  }
   
   func click(_ text: String) {
     switch text {