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IOS Q&A -The Basics#01

IOS Interview Questions and Answers

The Basics#01


1. What are the Key Features of the Swift programming language?
  • Modern: Swift is a result of the latest research on programming languages, combined with decades of experience building Apple platforms. Also, Swift is continuously evolving.
  • Safe: Swift is a type-safe language which means, If we pass a String to a variable of type Int by mistake, then Swift throws a compile-time error. Also, it’s a static programming language i.e. any variable or a constant should be declared or inferred to a specific type at the compile time.
  • Fast: Swift was built to be fast using the incredibly high-performance LLVM compiler technology. There are claims that Swift is 2.6x faster than Objective-C and 8.4x faster than Python.
  • Expressive: Swift is called Syntactic sugar because it makes the language “Sweeter” for developer use. Swift offers a simplified syntax and grammar that is easy to read and write.
  • Open source: In 2015, Swift was open-sourced to encourage community-driven development of the language itself.

 2. What are types in swift?

In Swift, there are two kinds of types: Named types and Compound types.

A Named type is a type that can be given a particular name when it’s defined. Named types includes classes, structures, enumerations, protocols, arrays, dictionaries, optional values 
and user-defined named types etc,.

A Compound type is a type without a name, defined in the Swift language itself. There are two compound types: function types and tuple types.

3. How Swift ensures safety?
  • Swift eliminates entire classes of unsafe code.
  • Variables are always initialized before use.
  • Integers are checked for overflow.
  • Array indices are checked for out-of-bounds errors.
  • By default Swift objects can never be nil. Optionals ensure that nil values are handled explicitly.
  • Error handling allows controlled recovery from unexpected failures.
  • Swift heavily leverages value types, especially for commonly used types like Arrays and Dictionaries. Value types are quite safe while accessing in thread & memory.
  • Memory is managed automatically, and enforcement of exclusive access to memory guards against many programming mistakes.

4. What are the major differences between Swift and Objective-C?

No
Characteristics
Swift
Objective-C
1
Speed
Faster
Slower
2
Syntax
Syntactic sugar
Syntactically verbose and complex
3
Type
Static & Strongly typed
Dynamic typed
4
ARC
Full ARC support
Some API doesn’t support ARC
5
License
Apache open-source
GPL (General Public License)
6
Nil Handling
Optionals are better way to handle nil values.
The ability to send a message on a nil object without crashing might lead to bugs
7
Type inference
Yes. Also support explicit types.
No.
Need to specify the type explicitly.
8
Namespacing
Better support
Since Objective-C is built on top of C, it lacks namespacing. All classes in an Objective-C application should be globally unique.Hence UI, NS prefixes are used to make classes unique.
9
Tuples
Multiple return types using tuples
Can’t return multiple values
10
Pointers
No such thing as a traditional pointer in swift.
But there’s a way, using Unsafe Pointers.
Explicit pointers exist.
11
Functional Programming Patterns
Swift incorporates a number of functional programming features, such as map and filter.Also it is easy to create user defined higher order functions using extensions.
Objective-C has no built-in support for functional programming.
12
Enums
Enums are very powerful in swift, then can contain methods and be passed by value. Also, Indirect statement allows enums to refer to itself.
Typical C type enums
13
Guard & Defer
Guard statements are most useful when combined with optional bindings.

A defer block is executed just before the control transferred out of the current scope.
No
14
String Manipulation
Better support with String interpolation. No need to worry about mutability.
String manipulation like concatenation,interpolation, formatting etc,. is cumbersome.



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