WorldTrotter

This is a simple iOS app that converts temperature value from degrees Fahrenheit to degrees Celsius along with a map view and a web view in a tab bar setup and provides Spanish and Korean language and region support.

Getting Started

This project was created to gain a better understanding of views and the view hierarchy, and how views are laid out using Auto Layout and to learn about UITabBarController and UISegmentedControl. The project also explores Localizable Strings, string tables and NSLocalizedStrings for internationalization and localization.

App Walkthrough GIF

This GIF shows the app in action (preventing multiple decimal separators, the background color in the conversion view changes in each visit, the decimal separator sign changes from a period to a comma for the Spain region selection, the language changes for Spanish selection in both the conversion view and the map view, and the language changes again for Korean selection and the decimal separator changes for the South Korea region selection)

NOTE: the "Tap for Location" button in the map view is for zooming in on the user's location when the app is running on an actual device and the user has granted location permission!

Lessons Learned

1. Every application has a singleton instance of UIWindow that serves as the superview of all the views in the application. UIWindow is a subclass of UIView.
2. A view's frame specifies the view's size and its position with respect to its superview. A view's bounds, on the other hand, is described with respect to itself. If a view's frame is {x:20, y:20, width: 50, height: 50}, that means this view's top-left corner is placed at the point (20, 20) in it's superview's coordinate system. That same view's bounds would be {x: 0, y: 0, width: 50, height: 50}.
3. To programmatically create and add views, initalize a UIView instance with a desired CGRect properties. Then, this instance could be added to an existing container view.
4. UIColor class has computed properties for common colors such as blue, green, black, clear etc.
5. All the numbers that define a UIView instance's dimensions and location are points, NOT pixels. Points are used for sizes, positions, lines and curves to enforce consistency across displays of different resolutions.
6. The Auto Layout system utilizes layout attributes of a UIView instance to determine it's alignment rectangle. The layout attributes are height, width, top, bottom, left, right, centerX, centerY, firstBaseline, lastBaseline, leading, trailing etc.
7. The frame of a UIView encompasses the entire view while the alignment rectangle only contains the portion to be used for alignment purposes.
8. A constraint is used to determine a layout attribute of one or more UIView instances in a view hierarchy. At least two constraints are needed per dimension.
9. A UIView instance will usually look for the nearest neighbor in the specified direction of a constraint, which is usually the closest sibiling UIView instance in that direction. If no such sibiling exists, its superview will become the nearest neighbor.
10. The intrinsic content size of a UIView object can reduce the need for explictily adding height and width constraints. For example, the intrinsic content size of a UITextField will be the size of the text rendered for the specified font.
11. The keyboard to appear for a UITextField instance can be modified using the autoCapitalizationType, autoCorrectionType, spellCheckingType, keyboardType, keyboardAppearance, returnKeyType properties. These correspond to properties of the UITextInputTraits protocol that the UITextField class adopts.
12. To dismiss the keyboard of a UITextField instance based on a user tap on the background view, set up an action method to be triggered from the tap and then call resignFirstResponder() on that instance.
13. A property observer can execute code whenever a property's value changes and is declared using curly braces immediately after the property declaration. They are declared using either willSet and didSet.
14. To customize the display of a number, like how many numbers after decimal, use a NumberFormatter instance. Similarly, there are DateFormatter, LengthFormatter, MassFormatter, EnergyFormatter etc. formatter classes.
15. Delegation is use to address callbacks in object-oriented programming. In advance of an event, a callback function is supplied and is called during each occurrence of the event. For any instance to become a delegate of a specific type, that instance must conform to the specific type's delegate protocol. For example, for a UIViewController instance to be a UITextField delegate, that instance must conform to UITextFieldDelegate protocol by adding UITextFieldDelegate in the comma-delimited list of its declaration.
16. Using lazy loading optimization, a view controller's view is not loaded until it appears on the screen. So, the loadView() and the viewDidLoad() methods of a view controller are only called once it's view appears.
17. To programmatically create a UIViewController instance's view hierarchy, use the loadView() method.
18. If a framework is optimized out by the compiler, it could still be included in the project by adding that framework to the Linked Frameworks and Libraries in the project settings.
19. The initial view controller of the main interface, which corresponds to Main.storyboard, gets set as the value for the rootViewController property of the app's singleton UIWindow instance.
20. UITabBarController is useful for presenting a UI that allows the user to switch between multiple views. Essentially, a UITabBarController object keeps an array of view controllers and maintains a tab bar with UITabBarItem objects at the bottom of the screen.
21. When using programmatic constraints, set the UIView instance's translatesAutoResizingMaskIntoConstraints to false. The translated constraints that iOS creates by default to match autoresizing masks will often cause conflict with the explicit contraints.
22. Any progmmatically added constraint must be explicitly activated by setting its isActive property to true.
23. The different layout attributes mentioned earlier are defined by the NSLayoutConstraint class's NSLayoutConstraint.Attribute constant. The NSLayoutConstraint.Attribute enum has cases for each attribute.
24. To create a side by side options in a panel like view, use UISegmentedControl. This is a subclass of UIControl, just like UIButton, UITextField etc.
25. Internationlization and localization are the two important parts of making an app friendly to a global audience. Internationalization refers to making the app not rely on any hardcoded information, such as currency, date format etc. Localization, on the other hand, refers to the app's ability to be implemented in multiple languages and in differnt info formats based on the user's Language and Region settings.

License

Copyright 2019 Soumik Barua

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.