Swift Interview Questions and Answers

Swift is the latest, open source programming language from Apple, which is very easy to learn. The language is available for developing OS X, iOS, and watchOS apps. It allows developers to prototype and write apps faster and with fewer bugs than ever before.

Swift 5.0

Yes, It is a very powerful, intuitive open source programming language developed by Apple for iOS, macOS, watchOS, tv OS, and Linux etc.

Functions

• Self-contained code that performs a specific task.
• Identified by their name to call whenever a task is required.
• To declare a function, use func.
• Use . -> to separate function parameters parenthesis and return type.

Methods

• Associated with a particular type.
• The first parameter name is given by default.
• Enumeration and Structure define methods.

Three collection types are available - Arrays, Sets and Dictionaries. These are used to store different collections of values. These three collection types are mutable and are clear about the types of keys and values associated with them.

You can make a property optional by declaring a question mark “?” in the code. If a property does not hold any value, then this symbol “?” can help in avoiding runtime errors.

It is fast, safe, modern, and enables a level of interactivity in development. Swift Programming contains a number of features such as closures, generics, and type inference that make it much easier to use.

• Safer, faster and more powerful
• Can co-exist alongside Objective-C
• Innovative features
• It offers Interactive Coding styles
• APIs are easier to maintain and read
• One of the best ways to code OS X and IOS apps

The multiline comment enables the programmer to comment out large blocks of code easily.
A forward slash, an asterisk and then a colon is opening comment - (/*:)
An asterisk and forward slash is a closing comment – (*/))

When you are trying to perform extra clean-up of your classes, you can define a block called deinit.
Here is the Syntax:
deinit {
    //Your cleanup statement here.
}

Swift -

• No need to finish code with a semi-colon.
• The syntax is simple and clear.
• Does not allow multiple inheritance.

Objective-C

• Need to finish code with a semi-colon.
• The syntax is difficult to master.
• Allows multiple inheritance.

It is the process of creating an instance of class, enumeration or structure. It involves setting an initial value for the existing property and performing initialization before the new instance is available for use. The initialization process can be done by defining initializers.

UI in Swift are connected similar to the way we do in Objective-C. Binding process is the same, only core level has changed. You can select button/label on xib file and bind as is it.

Open the storyboard file in Xcode and drag in a “Table View” object from the Library. Position it full screen and make sure the edges line up. Now, adjust the height by dragging the edge and creating space at the top. Try running the app in the simulator and you shall see an empty table view.

Floating point numbers have a fractional component and they represent a greater range of values than integer types.

There are two kinds of floating point numbers – Double and Float.
Double represents a 64-bit floating point number. It is used when values are large.
Float represents a 32-bit floating point number. It is used when values do not need 64-bit precision.

It is a process of querying and calling various properties. You can chain multiple queries together, but if any link is nil, the entire chain will fail.

The classes in Swift are not inherited from the base class. If you define any class without specifying its superclass, it automatically becomes the base class.

Any property whose initial values are not calculated until the first time it is used is called a lazy stored property. Such properties can be declared by writing the lazy modifier. These properties are useful when the initial value of a property is dependent on external factors whose values are unknown.

• Supports all kinds of data and checks for equality.
• When a case is matched, the program exits from the switch and does not continue to check.
• Switch statements must be exhaustive, and you must cover all possible values for the variable.
• No break is required because there is no fallthrough.

The way to handle errors in Swift is different from Objective-C. In Swift, you can declare that a function has thrown an error. A function that calls this method must do it from a try block. It is the caller's responsibility to handle the error. This process is quite similar to how we handle errors in Java.

These are control flow statements that can be a great addition if you are doing defensive style programming. These statements evaluate a boolean condition and proceed with the execution only if the evaluation is real. Such statements always have an else clause.
guard let courses = student.courses! else {
   return
}

Swift has five access levels: open access, public access, internal access, file-private access, and private access. Open access is the highest access level and private access is the lowest access level. Almost all entities, except a few, have default internal access levels.

Adapter pattern allows the classes with incompatible interfaces to work together. An adapter pattern wraps itself around the object to show a standard interface for interacting with that object.
Memento pattern is used in iOS as a part of state restoration. These patterns are especially used for archiving in Apple.

It is a group of values represented as one value, which can be used to return multiple values from a single function call.

Tuple are of two types - Named and Unnamed.

Encodable protocols take instances of our objects and turn them into data. That data can be stored it to the files or sent to the server.
Decodable protocols allow us to take data and create instances of our objects and pass down from the server.

3 reasons inheritance is not good:

• You cannot use superclasses or inheritance with Swift value types.
• Upfront modeling
• Customization is vague.