Click the Object library button to shows the Object library. You can then choose any of the UI objects, and drag-and-drop them into the view. If you're in the icon view mode of the Object library, you can click on any of the objects to reveal the detailed description. Okay, it's time to add a button to the view. All you need to do is drag a Button object from the Object library to the view. As you drag the Button object to the view, you'll see a set of horizontal and vertical guides if the button is centered. Stop dragging, and release your button to place the Button object there.
Next, let's rename the button.
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To edit the label of the button, double-click it and name it "Hello World". After the change, you may need to center the button again. You're now ready to test your app. Select the iPhone 8 simulator and hit the Run button to execute the project, you should see a Hello World button in the simulator as shown in figure Cool, right? However, when you tap the button, it shows nothing.
We'll need to add a few lines of code to display the "Hello, World" message. Now that you've completed the UI of the HelloWorld app, it's time to write some code. In the project navigator, you should find the ViewController. This file is actually associated with the view controller in the storyboard. In order to display a message when the button is tapped, we'll add some code to the file. If you have written code in Objective-C before, one big change in Swift is the consolidation of header. All the information of a particular class is now stored in a single. Select the ViewController. Type the following lines of code in the ViewController class:.
The Swift code within the method is new to you. I will explain it to you in the next chapter. Meanwhile, just consider the showMessage sender: UIButton as an action. When this action is called, the block of code will instruct iOS to display a "Hello World" message on screen. You can try to run the project in the simulator. The behaviour of the app is still the same. When you tap the button, it still doesn't show you any response. The reason is that we haven't made the connection between the button and the code.
I said before that the beauty of iOS development is the separation of code. But how can we establish the relationship between our source code and the user interface? You need to establish a connection between the "Hello World" button and the showMessage sender: UIButton method you've just added, such that the app responds when someone taps the Hello World button.
Now select Main.
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Press and hold the control key of the keyboard, click the "Hello World" button and drag it to the View Controller icon. Select it to make a connection between the button and showMessageWithSender: action. That's it! You're now ready to test your first app. Just hit the Run button. If everything is correct, your app should run properly in the simulator.
This time, the app displays a welcome message when you tap the Hello World button. As mentioned before, you do not need to write code to customize a UI control. Here, I want to show you how easy it is to change the properties e. Select the "Hello World" button and then click the Attributes inspector under the Utility area. You'll be able to access the properties of the button.
Here, you can change the font, text color, background color, etc. Try to change the text color under Button section to white and background scroll down and you'll find it under View section to red or whatever color you want. Not only can you change the color of a button, you can modify the font type and size in the Attributes inspector by setting the Font option. Your task is to continue to work on the project and create a user interface like figure When a user taps any of the buttons, the app displays the same Hello World message.
Wouldn't it be great if you can display the meaning of the emoji icon instead of the same "Hello World" message like what I have shown you in figure ? You've learned how to use a dictionary to store the meaning of emoji icons.
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Now try to modify the showMessage sender: UIButton method such that it displays the meaning of the emoji icon. I will give you a hint. Here is the code skeleton. Replace the code of your existing showMessage sender: UIButton method with the following and fill in the missing code:.
This exercise is more difficult than the first one. Try your best to complete it. It is really fun to see that you turn a Hello World app into a simple Emoji Translator. You've built your first iPhone app. It's a simple app, but I believe you already have a better understanding of Xcode and understand how an app is built. It's easier than you thought, right?
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Even if you couldn't complete exercise 2, that is completely fine. Don't be discouraged. I have included the solution for your reference. Just keep reading, you will get better and better as you have more coding practices. In the next chapter, we'll discuss the details of the Hello World app and explain how everything works together.
To continue reading and access the solution of the exercise, please get the full copy of the book here. Chapter 3 Hello World! Theory is nice but nothing replaces actual experience. Despite its simplicity, the "Hello World" program serves a few purposes: It gives you an overview of the syntax and structure of Swift, the new programming language of iOS.
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