Commit 0835100

@@ -0,0 +1,6 @@
+#import <Foundation/Foundation.h>
+
+@interface Brain : NSObject
+-(void) addObject:(double)operand;
+-(double) performOperation:(NSString *)operation;
+@end

@@ -0,0 +1,59 @@
+#import "Brain.h"
+
+@interface Brain()
+@property (strong, nonatomic) NSMutableArray * arrOperands;
+@end
+
+@implementation Brain
+-(void) addObject:(double)operand
+{
+  if (!self.arrOperands)
+  {
+    self.arrOperands = [[NSMutableArray alloc] init];
+  }
+
+  [self.arrOperands addObject:[NSNumber numberWithDouble:operand]];
+}
+
+-(double) performOperation:(NSString *)operation
+{
+  double result = 0;
+
+  if (self.arrOperands.count > 1)
+  {
+    if([operation isEqualToString:@"+"])
+    {
+      result = [self removeLastObject] + [self removeLastObject];
+    }
+
+    if ([operation isEqualToString:@"-"])
+    {
+      result = -[self removeLastObject] + [self removeLastObject];
+    }
+
+    if ([operation isEqualToString:@"x"])
+    {
+      result = [self removeLastObject] * [self removeLastObject];
+    }
+
+    if ([operation isEqualToString:@"/"] && [[self.arrOperands lastObject] doubleValue] != 0)
+    {
+      double tempDivisor = [self removeLastObject];
+      result = [self removeLastObject] / tempDivisor;
+    }
+  }
+
+    [self addObject:result];
+    return result;
+}
+
+-(double) removeLastObject
+{
+  NSNumber * lastObject = [self.arrOperands lastObject];
+  if (self.arrOperands)
+  {
+    [self.arrOperands removeLastObject];
+  }
+  return [lastObject doubleValue];
+}
+@end

@@ -1,7 +1,10 @@
 #import <UIKit/UIKit.h>
 
+@class Brain;
+
 @interface ViewController : UIViewController
 @property (strong, nonatomic) IBOutlet UILabel * display;
+@property (strong, nonatomic) Brain * myBrain;
 -(IBAction) numberPressed:(id)sender;
 -(IBAction) operationPressed:(id)sender;
 -(IBAction) enterPressed:(id)sender;

@@ -1,7 +1,8 @@
 #import "ViewController.h"
+#import "Brain.h"
 
 @interface ViewController ()
-
+@property BOOL enteringNumber;
 @end
 
 @implementation ViewController
@@ -9,6 +10,10 @@
 - (void)viewDidLoad
 {
     [super viewDidLoad];
+    if (!self.myBrain)
+    {
+      self.myBrain = [[Brain alloc] init];
+    }
 	// Do any additional setup after loading the view, typically from a nib.
 }
 
@@ -20,13 +25,30 @@
 
 -(IBAction) numberPressed:(UIButton *)sender
 {
+  NSString * number = sender.currentTitle;
+  if (self.enteringNumber)
+  {
+    self.display.text = [self.display.text stringByAppendingString:number];
+  }
+  else
+  {
+    self.display.text = number;
+    self.enteringNumber = YES;
+  }
 }
 
 -(IBAction) operationPressed:(UIButton *)sender
 {
+  if(self.enteringNumber)
+  {
+    [self enterPressed:(UIButton *)sender];
+  }
+  self.display.text = [NSString stringWithFormat:@"%g", [self.myBrain performOperation:sender.currentTitle]];
 }
 
 -(IBAction) enterPressed:(id)sender
 {
+  [self.myBrain addObject:[self.display.text doubleValue]];
+  self.enteringNumber = NO;
 }
 @end

@@ -23,6 +23,7 @@
 		CD4CBEFE174B20A900B6DA7C /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = CD4CBED9174B20A900B6DA7C /* Foundation.framework */; };
 		CD4CBF06174B20A900B6DA7C /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = CD4CBF04174B20A900B6DA7C /* InfoPlist.strings */; };
 		CD4CBF09174B20AA00B6DA7C /* CalculatorTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CD4CBF08174B20AA00B6DA7C /* CalculatorTests.m */; };
+		CDAF0243174B25850088CE1A /* Brain.m in Sources */ = {isa = PBXBuildFile; fileRef = CDAF0242174B25850088CE1A /* Brain.m */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -58,6 +59,8 @@
 		CD4CBF05174B20A900B6DA7C /* en */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = en; path = en.lproj/InfoPlist.strings; sourceTree = "<group>"; };
 		CD4CBF07174B20AA00B6DA7C /* CalculatorTests.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = CalculatorTests.h; sourceTree = "<group>"; };
 		CD4CBF08174B20AA00B6DA7C /* CalculatorTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = CalculatorTests.m; sourceTree = "<group>"; };
+		CDAF0241174B25850088CE1A /* Brain.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = Brain.h; sourceTree = "<group>"; };
+		CDAF0242174B25850088CE1A /* Brain.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = Brain.m; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -122,6 +125,8 @@
 				CD4CBEEF174B20A900B6DA7C /* ViewController.h */,
 				CD4CBEF0174B20A900B6DA7C /* ViewController.m */,
 				CD4CBEF2174B20A900B6DA7C /* ViewController.xib */,
+				CDAF0241174B25850088CE1A /* Brain.h */,
+				CDAF0242174B25850088CE1A /* Brain.m */,
 				CD4CBEDE174B20A900B6DA7C /* Supporting Files */,
 			);
 			path = Calculator;
@@ -273,6 +278,7 @@
 				CD4CBEE4174B20A900B6DA7C /* main.m in Sources */,
 				CD4CBEE8174B20A900B6DA7C /* AppDelegate.m in Sources */,
 				CD4CBEF1174B20A900B6DA7C /* ViewController.m in Sources */,
+				CDAF0243174B25850088CE1A /* Brain.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -453,6 +459,7 @@
 				CD4CBF0E174B20AA00B6DA7C /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 		CD4CBF0F174B20AA00B6DA7C /* Build configuration list for PBXNativeTarget "CalculatorTests" */ = {
 			isa = XCConfigurationList;
@@ -461,6 +468,7 @@
 				CD4CBF11174B20AA00B6DA7C /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 /* End XCConfigurationList section */
 	};