Control-click or right-click the button in the storyboard again, and drag the pointer into the ViewController class definition. When the Connection dialog appears, select Action from the Connection dropdown menu. In this example, your entry in the Name field doesn't define a variable. Instead, the Name field defines the action that is connected to the button tap event.
Name the action: buttonPressed. Click the Connect button to finalize the creation of the action. You now have a function to execute when the user taps the button. Add the following line inside the buttonPressed function:. This code prints a message to the Xcode console when the function executes. Build and run your app, and then click the button to see the message print in the console at the bottom-right of the screen. Back in the Document Outline, select the button again, and then select the Connections inspector in the utilities area.
Now that you've connected an outlet and an action to the button, you'll see this outlet and action in the Connections inspector. Every attribute in Interface Builder represents a property that can also be configured programmatically, or in code. Interface Builder is simply a graphical user interface for configuring and setting properties on UIKit classes your app displays. Notice that each setting in Interface Builder has a companion property.
Many objects that you can configure in Interface Builder have properties that can only be set programmatically. For example, UIScrollView has a contentSize property that does not have a matching option in the Attributes inspector. When you need to adjust one of these settings, you can do so programmatically by setting up an IBOutlet and updating the properties using dot-notation:.
In fact, everything that you can do in Interface Builder can also be done programmatically, including setting up all child views and adding them to the screen:. This type of setup is most commonly done in the viewDidLoad method of a view controller, where you can access the view controller's view property before the view hierarchy appears on the screen. While you have the option to do everything programmatically, Interface Builder can save you time when setting up complex views.
As your projects become more complex, storyboards help you more easily maintain your interface setup. Additionally, Interface Builder has support for building complex views that support multiple device sizes, all in one place. The objective of this exercise is to use Interface Builder and the assistant editor to create a basic view. You should now have a simple view with text that you can edit in code.
Save your project to your project folder again. Here is the completed Interface Builder project. You can compare it to how you built your storyboard and used the Assistant Editor.
Please plan your activities around this required maintenance. Xcode Essentials. Time Estimate. Preview UIs without compiling the app. Outlets and Actions You often need to reference your visual elements in code so that these elements can be adjusted at runtime, or when the app is already running.
Creating an Outlet Control-click or right-click the button in the storyboard, and start dragging to the Assistant editor pane, which contains the ViewController class definition. The outlet definition has multiple parts.
They appear from left to right: Circle. The filled circle icon indicates that the outlet is connected. The circle is empty if the variable isn't connected to anything.
Unique to Interface Builder, this keyword specifies a relationship between the variable and a storyboard. Without the IBOutlet keyword, the circle doesn't appear. To turn on any of these constraints, enter the value desired and then click the faded red margin. It will turn deeper red, letting you know the constraint has been activated. Xcode will automatically select the nearest neighboring element for you.
This is my favorite method and the one I use the most often. Ctrl-drag allows you to set a constraint from one element to another element. To do this, hold ctrl on your keyboard, click the first element, then drag your cursor to the second element.
In the above example, I ctrl-clicked on the image view, then dragged it to the background image. The dialog will pop up like so:. This popup dialog displays constraints you can add. Any constraint with a dot next to it means that it already exists. Setting constraints is so difficult! Can I just drag my elements onto the screen and let Xcode handle the rest? You have a couple of options, you can Add Missing Constraints, Reset to Suggested Constraints or even just clear all the constraints.
I recommend understanding how constraints work and adding them yourself. To edit constraints, simply go into the Size Inspector. Underneath the Size Inspector, there is a constraints section.
Here you can click edit on any of the constraints and change its value. If you accidentally added a constraint, you can easily delete it. Select the element that has a constraint on it in the document outline. Constraint priority tells your application which constraints are more important. If your user interface gets into a position where it can only satisfy one of two constraints, the constraint with higher priority will be enforced and the other constraint will not be applied.
In this sense, constraints are not strict rules, but rules that may be broken to satisfy more other important rules.
Understanding this concept is essential to building more complex layouts. If you click the drop-down menu, Xcode will offer 3 presets. Required , High and Low I recommend you stick to these 3 options. Having too many different priority levels can quickly make your user interface difficult to debug. Constraint errors can lead to broken user interfaces. This could be because of multiple reasons:. Missing constraints occur when the auto-layout engine does not have enough information to build the user interface.
You can fix this by adding more constraints. Typically this error shows up in your interface builder in the form of red lines.
Looks like we need constraints for the width and height of our image card view. You can now see there are no more redlines in the interface builder and the red arrow in the document outline is gone.
For example, lets say you want something to be height of , but you also want it have the height of This will result in an error redlines in your interface builder. We can solve this by simply deleting one of the constraints. Click on one of the constraints in the conflicting constraints section, then hit the back button and hit delete on your keyboard.
This should get rid of the constraint and fix your conflict! Misplaced views result in a warning in your interface builder. This is characterized by yellow lines and a yellow warning error on your document outline. To fix this warning, you can either drag the view back into its proper position or click the Update Frames button in the bottom right corner.
I always use the Update Frames button because it saves me a lot of time and its just easier. Once you click that button, your views will be moved into the correct position and the warning should disappear :. These concepts should get you pretty far. I use these tips everyday in the industry. The next thing you should be familiar with is the Inspector Pane. This opens up the inspector pane on the right hand side of your workspace.
Here we have multiple tabs:. The file inspector is not often used in my experience. Target membership is important and having the 3 default checkboxes checked is important. Target membership is required to be specified in order for your project to build properly. Usually the default value is sufficient. Posted by wholl0p. Same issue on XCode 7 final release.
Need a remedy for this. Posted by callmeed. I found the solution. It works for me. Posted by Ukjeong Lee. What worked for me: In the project navigator click your app.
Hit the "General" tab and change your "Deployment Target" from 8 to 8. Hope this helps. Posted by robsmall. Posted by smileBot.
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