The sample shows how to setup the gestures in Xcode’s interface builder, rather than in Objective-C code. Using the UIPanGestureRecognizer we can allow [...]]]> In followup from my iPhone programming presentation I have uploaded the presentation and sample Xcode project (Xcode 4.3.2) The sample converts between temperatures in celsius and fahrenheit.

The sample shows how to setup the gestures in Xcode’s interface builder, rather than in Objective-C code. Using the UIPanGestureRecognizer we can allow sliding input for the temperature conversion. The only code we need to implement is the action to take in response to a detected gesture.

Download the slides and sample code:

• iOS Development AppRochester 4-3-12
• AppRochester Sample Xcode Project

The biggest hassle in testing is setting up the [...]]]> Xcode 4 has drastically improved iPhone unit testing and Mac unit testing from my previous post, iPhone Unit Testing Explained – Part I Creating the unit testing target is easy and you can start writing test code in under 5 minutes.

The biggest hassle in testing is setting up the project correctly, and Xcode 4 makes it simple. If you read Part I, I pushed for GHUnit because of the GUI interface, but now Xcode’s built in testing is enough to get you started. If you need a GUI, add GHUnit later, but start writing your tests today, since they’re compatible with GHUnit when you decide to integrate with it.

Testing is important to start from the beginning or you will never have the motivation to write the tests unless your boss demand

Getting Started

To start writing unit tests you have two options, either create a new project with unit tests or add unit tests to an existing project.

New Project with Unit Tests

Create a new project and make sure the checkbox is enabled for unit tests.

Add Unit Tests Target to Existing Projects

Add a unit test target to your project by clicking on your Project (top left) -> Add Target (bottom middle) -> iOS -> Other -> Unit Testing Bundle.

(Optional) Share the Target and Testing Scheme

If you add a unit test target, you’ll most likely want to share your testing scheme with your team over version control (git, svn, etc.) Otherwise you’re teammates will have to setup for themselves.

Goto Editor -> Manage Schemes -> Click Shared next to the Unit Test

Adding Resources

When you want to test code or import resources like images or data files you’ll need to tell the testing target about the resources. There are two ways, you can do it when you first add the resource to the project or you can do it by editing the Build Phases for the unit test target.

Adding New Resources to the Unit Test Target

Click on File -> Add Files to “TestProject” -> Click on the checkbox on unit test target and Copy items

Adding Existing Resources to the Unit Test Target

Click on your project “TestProject” -> Build Phases -> Expand one of three (Compile Sources, Link Binary With Libraries, or Copy Bundle Resources)

Resource Paths are Different!

Many assumptions that your bundle is the main bundle will cause problems when testing. (Especially when adding tests to existing code) Look at the difference in bundles, the main bundle isn’t what you’d expect in a unit test.

NSString *mainBundlePath = [[NSBundle mainBundle] resourcePath];

NSString *directBundlePath = [[NSBundle bundleForClass:[self class]] resourcePath];

NSLog(@”Main Bundle Path: %@”, mainBundlePath);

NSLog(@”Direct Path: %@”, directBundlePath);

NSString *mainBundleResourcePath = [[NSBundle mainBundle] pathForResource:@”Frame.png” ofType:nil];

NSString *directBundleResourcePath = [[NSBundle bundleForClass:[self class]] pathForResource:@”Frame.png” ofType:nil];

NSLog(@”Main Bundle Path: %@”, mainBundleResourcePath);

NSLog(@”Direct Path: %@”, directBundleResourcePath);

Output:

Main Bundle Path: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.1.sdk/Developer/usr/bin

Direct Path: /Users/paulsolt/Library/Developer/Xcode/DerivedData/PhotoTable-dqueeqsjkjdthcbkrdzcvwifesvl/Build/Products/Debug-iphonesimulator/Unit Tests.octest

Main Bundle Path: (null)

Direct Path: /Users/paulsolt/Library/Developer/Xcode/DerivedData/PhotoTable-dqueeqsjkjdthcbkrdzcvwifesvl/Build/Products/Debug-iphonesimulator/Unit Tests.octest/Frame.png

Problem: My Unit test has a nil image, data file, etc. Why?

The unit test doesn’t use the same bundle for resources that you’re accustomed to when running an app. Therefore, the resource we’re trying to load cannot be found.  You’ll need to make changes to the code to support testing external resources (images, data files, etc). For example the following code

- (UIImage *)resizeFrameForImage:(NSString *)theImageName {

UIImage *image = [UIImage imageNamed:theImageName];

// ... do magical resize and return

return image;

}

Solution 1: Change the function parameters

Functions like these are semi-black boxes that aren’t ideal for testing. You want access to all your inputs/outputs, especially if we’re working with any kind of file resource. To fix it, just pass in the resource from the unit test, rather than having the function load it from a NSString object.

- (UIImage *)resizeFrameForImage:(UIImage *)theImage {

// ... do magical resize and return

return theImage;

}

Solution 2: Change the resource loading inside the function

If you need to load the resource in the function, you can alternatively change the way it is loaded. You need to stop using UIImage’s imageNamed: method and switch to imageWithContentsOfFile: This way you can pass in the resource with the correct path, however it’ll change logic elsewhere in your app.

- (UIImage *)resizeFrameForImage:(NSString *)theImagePath {

UIImage *image = [UIImage imageWithContentsOfFile:theImagePath];

// ... do magical resize and return

return image;

}

Solution 3: Load resources using the bundle for the current class

- (UIImage *)resizeFrameForImage:(NSString *)theImageName {

// Note: There are several ways you can write it, but make sure you include

//  the extension or you'll have trouble finding the resource

// 1. NSString *imagePath = [[NSBundle bundleForClass:[self class]] pathForResource:@"Image.png" ofType:nil];

// 2. NSString *imagePath = [[NSBundle bundleForClass:[self class]] pathForResource:@"Image" ofType:@"png"];

NSString *imagePath = [[NSBundle bundleForClass:[self class]] pathForResource:theImageName ofType:nil];

UIImage *image = [UIImage imageWithContentsOfFile:imagePath];

// ... do magical resize and return

return image;

}

My First Test

Code completion in Xcode will make writing tests easy. To test different things you’ll use the following macros:

• STAssertNotNil(Object, Description);
• STAssertEquals(Value1, Value2, Description);
• STAssertEqualObjects(Object1, Object2, Description);

Example: MyTest.m

@implementation TestImagePrintHelper

- (void)setUp

{

[super setUp];

// Set-up code here.

}

- (void)tearDown

{

// Tear-down code here.

[super tearDown];

}

- (void)testName {

NSString *testFirstName = @"Paul";

STAssertEqualObjects([person firstName], testFirstName, @"The name does not match");

}

@end

The STAssertEqualObjects macro will invoke the object’s isEqual method, make sure you write one. See the section below. If you used the STAssertEquals it will test for primitive/pointer equality, not object equality.

Testable Code

Writing testable code requires that you add some additional functions that might feel optional before you decided to start testing.

1. Create a isEqual method for your class.

Most of the time you’ll want to compare if the object is the correct object. This always requires that you write an isEqual method, otherwise you’ll be using the NSObject isEqual test and it’ll compare address pointers for the objects.

Example: Person.m

- (BOOL)isEqual:(id)other {

if (other == self) { // self equality, compare address pointers

return YES;

}

if (!other || ![other isKindOfClass:[self class]]) { 

// test not nil and is same type of class

return NO;

}

return [self isEqualToPerson: other]; // call our isEqual method for Person objects

}

- (BOOL)isEqualToPerson:(Person *) other {

BOOL value = NO;

if (self == other) { // test for self equality

value = YES;

 } elseif([[selffirstName] isEqualToString:[other firstName]] &&

[self age] == [other age]) {

// Add any other tests for instance variables (ivars) that need to be compared

value = YES;

}

return value;

}

2. Create a description method for your class.

This is what will output on the command line, rather than the objects memory address. It can be also called when you decide to print the value in a tests

Example: Person.m

- (NSString *)description {

return [NSStringstringWithFormat:@"Person Name: %@ Age: %d", [self firstName], [self age]];

}

Example: Test using the description method, and we’ll see the first name and age printed like it was formatted in our description method.

STAssertEqualObjects([personfirstName], testFirstName, @"The name does not match %@", person);

Further reading in Apple’s Unit Testing Guide is available. Now you have the basics for unit testing. The next part will provide an example project using resources and providing unit tests.

(Part III: Coming Soon)

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About this Class

Learn how to get started [...]]]> I’m teaching a small hands-on course for iPhone development in Rochester, NY on April 21st 10am-12pm.

Signup

Space is limited: http://skl.sh/rIUWEE

About this Class

Feature article by MD

Update: 8/31/11 Idea to App Store Slides (PDF)

iPhoneOS Development III – Paul Solt

Gestures Demo

Here’s the basic math:

1. We know: currentSize * scaleFactor = newSize

2. Clamp the maximum scale factor [...]]]> After wasting two days I’ve finally figured out how to correctly limit zoom levels when working with a UIPinchGestureRecognizer. I needed to resize images, but I didn’t want people to go outside of desirable limits.

Here’s the basic math:

1. We know: currentSize * scaleFactor = newSize

2. Clamp the maximum scale factor using the proportion maxScale / currentScale

3. Clamp the minimum scale factor using the proportion minScale / currentScale

The code below assumes there is an instance variable CGFloat lastScale and that a view has been set for the UIPinchGestureRecognizer.

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer {
 
if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
// Reset the last scale, necessary if there are multiple objects with different scales
lastScale = [gestureRecognizer scale];
}
 
if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
[gestureRecognizer state] == UIGestureRecognizerStateChanged) {
 
CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];
 
// Constants to adjust the max/min values of zoom
const CGFloat kMaxScale = 2.0;
const CGFloat kMinScale = 1.0;
 
CGFloat newScale = 1 -  (lastScale - [gestureRecognizer scale]); // new scale is in the range (0-1)
newScale = MIN(newScale, kMaxScale / currentScale);
newScale = MAX(newScale, kMinScale / currentScale);
CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
[gestureRecognizer view].transform = transform;
 
lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call
}
}

http://www.youtube.com/watch?v=xkwE8BRQsAo