Tips, tricks & notes about Apple's Swift;
- Functions - Use func to declare a function. Call a function by following its name with a list of arguments in parentheses. Use -> to separate the parameter names and types from the function’s return type.
- Functions can also take a variable number of arguments, collecting them into an array - func sumOf(numbers: Int...) -> Int {
- Functions can be nested. Nested functions have access to variables that were declared in the outer function. You can use nested functions to organize the code in a function that is long or complex.
- Functions are a first-class type. This means that a function can return another function as its value.
- Functions are actually a special case of closures: blocks of code that can be called later. The code in a closure has access to things like variables and functions that were available in the scope where the closure was created, even if the closure is in a different scope when it is executed
- Closures are self-contained blocks of functionality that can be passed around and used in your code.
- You can write a closure without a name by surrounding code with braces ({}). Use in to separate the arguments and return type from the body.
- Single statement closures implicitly return the value of their only statement - let mappedNumbers = numbers.map({ number in 3 * number })
- A closure passed as the last argument to a function can appear immediately after the parentheses. When a closure is the only argument to a function, you can omit the parentheses entirely - let sortedNumbers = numbers.sort { $0 > $1 }
- Use class followed by the class’s name to create a class. A property declaration in a class is written the same way as a constant or variable declaration, except that it is in the context of a class. Likewise, method and function declarations are written the same way.
- Use an initializer to set up the class when an instance is created. Use init to create one.
- init(name: String)self.name = name}
- Notice how self is used to distinguish the name property from the name argument to the initializer.
- Completion Handlers, used for closures in many functions (see AlertViews) - good post This is the BEST tutorial I found, it hs all the flavors - http://sourcefreeze.com/uialertcontroller-ios-8-using-swift/
- Alert screens, used for popups & User instruction - good tutorial
- You use this representation to create an adaptive interface, which is an interface that automatically adjusts so that it looks good in the context of the current device and orientation.
- var window: UIWindow? - the question mark means it's optional ( ie it may not exist ie (may be nil))
- variables are mutable -
var myVariable = 42 - constants are immutable -
let myConstant = 42
AppDelegate class is where you write your custom app-level code.
Singleton - Swift - ObjectiveC migration
Singletons provide a globally accessible, shared instance of an object. You can create your own singletons as a way to provide a unified access point to a resource or service that’s shared across an app, such as an audio channel to play sound effects or a network manager to make HTTP requests.
Importing Objective-C into Swift - To import a set of Objective-C files in the same app target as your Swift code, you rely on an Objective-C bridging header to expose those files to Swift. Xcode offers to create this header file when you add a Swift file to an existing Objective-C app, or an Objective-C file to an existing Swift app.
Migration - Migration methodology
Provides an opportunity to revisit an existing Objective-C app and improve its architecture, logic, and performance by replacing pieces of it in Swift. For a straightforward, incremental migration of an app, you’ll be using the tools learned earlier—mix and match plus interoperability. Mix-and-match functionality makes it easy to choose which features and functionality to implement in Swift, and which to leave in Objective-C. Interoperability makes it possible to integrate those features back into Objective-C code with no hassle. Use these tools to explore Swift’s extensive functionality and integrate it back into your existing Objective-C app without having to rewrite the entire app in Swift at once
NSUserDefaults - Migration methodology
class NSUserDefaults : NSObject
Description
The NSUserDefaults class provides a programmatic interface for interacting with the defaults system. The defaults system allows an application to customize its behavior to match a user’s preferences. For example, you can allow users to determine what units of measurement your application displays or how often documents are automatically saved. Applications record such preferences by assigning values to a set of parameters in a user’s defaults database. The parameters are referred to as defaults since they’re commonly used to determine an application’s default state at startup or the way it acts by default.
The Auto Resolve Layout button displays the following selections;
Use - Reset to Suggested Constraints in ......... , to allow Xcode to resolve the constraints.
Small blue lines indicate that this view is properly laid out.
Orange lines & text indicate conflicting contraints that need fixing
This screenshot shows both the good (blue) & bad (orange) layouts described above.