Swift MCQs and Answers With Explanation: Swift is a modern and powerful programming language developed by Apple Inc. for building iOS, macOS, and other Apple platform applications. Swift is a popular choice among developers due to its simplicity, speed, and safety features. To help individuals assess their knowledge of Swift, we have compiled a list of the top 30 Swift MCQs. This Swift quiz consists of multiple choice questions and answers covering various topics related to Swift, such as its syntax, data types, control flow, and more.
Swift MCQs and Answers
The Swift MCQs and answers with explanations provide a useful resource for developers to evaluate their understanding of Swift and improve their skills in developing applications using the language.
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Swift Multiple Choice Questions and Answers
| Name | Swift |
| Exam Type | MCQ (Multiple Choice Questions) |
| Category | Technical Quiz |
| Mode of Quiz | Online |
Top 30 Swift MCQs
1. What is Swift’s type inference?
a. It allows developers to assign a variable without specifying its data type.
b. It allows developers to assign a variable with only one data type.
c. It allows developers to assign a variable with multiple data types.
d. It doesn’t allow developers to assign a variable without specifying its data type.
Ans: a. It allows developers to assign a variable without specifying its data type.
Explanation: Swift’s type inference allows developers to assign a variable without specifying its data type. The Swift compiler can deduce the data type of the variable based on the value assigned to it.
2. What is a closure in Swift?
a. A function that doesn’t have a name
b. A function that doesn’t take any arguments
c. A function that can capture and store references to any constants and variables from the context in which it is defined
d. A function that can only be called from within the same file
Ans: c. A function that can capture and store references to any constants and variables from the context in which it is defined
Explanation: A closure in Swift is a self-contained block of functionality that can be passed around and used in your code. Closures can capture and store references to any constants and variables from the context in which they are defined.
3. What is a protocol in Swift?
a. A blueprint for a class, struct, or enumeration
b. A way to define properties and methods for a specific type
c. A collection of related variables and functions
d. A way to organize code into reusable components
Ans: a. A blueprint for a class, struct, or enumeration
Explanation: In Swift, a protocol is a blueprint for a class, struct, or enumeration. It defines a set of properties, methods, and other requirements that a conforming type must implement.
4. What is the difference between a class and a struct in Swift?
a. A class is a reference type, and a struct is a value type.
b. A class can inherit from another class, and a struct can’t.
c. A class has a default initializer, and a struct doesn’t.
d. A class is used for storing data, and a struct is used for defining behavior.
Ans: a. A class is a reference type, and a struct is a value type.
Explanation: In Swift, a class is a reference type, meaning that multiple variables can refer to the same instance of the class. A struct, on the other hand, is a value type, meaning that when you create a new instance of a struct, a new copy of the data is created.
5. What is an optional in Swift?
a. A way to define a property that must have a value.
b. A way to define a property that may or may not have a value.
c. A way to define a property that can’t have a value.
d. A way to define a property that must have a default value.
Ans: b. A way to define a property that may or may not have a value.
Explanation: In Swift, an optional is a way to define a property or variable that may or may not have a value. You can use optionals to handle situations where a value may be nil, which can help avoid runtime errors.
6. What is the difference between let and var in Swift?
a. let is used for constants, and var is used for variables.
b. let is used for variables, and var is used for constants.
c. let is used for defining functions, and var is used for defining properties.
d. There is no difference between let and var in Swift.
Ans: a. let is used for constants, and var is used for variables.
Explanation: In Swift, let is used for defining constants, and var is used for defining variables. Constants are values that can’t be changed once they are set, while variables are values that can be changed.
7. What is the difference between an array and a set in Swift?
a. An array is an ordered collection of elements, and a set is an unordered collection of unique elements.
b. An array is an unordered collection of unique elements, and a set is an ordered collection of elements.
c. An array and a set are both ordered collections of elements, but an array can have duplicates, and a set can’t.
d. An array and a set are both unordered collections of elements, but an array can have duplicates, and a set can’t.
Ans: a. An array is an ordered collection of elements, and a set is an unordered collection of unique elements.
Explanation: In Swift, an array is an ordered collection of elements that can contain duplicates, while a set is an unordered collection of unique elements.
8. What is an enum in Swift?
a. A way to define a collection of related variables and functions.
b. A way to define a type that can have a limited number of values.
c. A way to define a function that takes a variable number of arguments.
d. A way to define a property that can have a default value.
Ans: b. A way to define a type that can have a limited number of values.
Explanation: In Swift, an enum is a way to define a type that can have a limited number of values. Enums are often used to represent a set of related options or states.
9. What is a guard statement in Swift?
a. A way to define a conditional statement that executes if a condition is true.
b. A way to define a loop that continues until a condition is true.
c. A way to define a conditional statement that executes if a condition is false.
d. A way to define a loop that breaks when a condition is false.
Ans: c. A way to define a conditional statement that executes if a condition is false.
Explanation: In Swift, a guard statement is a way to define a conditional statement that executes if a condition is false. Guard statements are often used to check for conditions that must be true in order for the rest of the code to execute.
10. What is a tuple in Swift?
a. A way to define a function that takes multiple arguments.
b. A way to define a type that can have a limited number of values.
c. A way to group multiple values into a single compound value.
d. A way to define a property that can have a default value.
Ans: c. A way to group multiple values into a single compound value.
Explanation: In Swift, a tuple is a way to group multiple values into a single compound value. Tuples can be useful for returning multiple values from a function or for passing multiple values as a single argument to a function.
11. What is a lazy property in Swift?
a. A property that must be initialized before it can be used.
b. A property that is computed on the fly every time it is accessed.
c. A property that is initialized only when it is first accessed.
d. A property that is never accessed or used.
Ans: c. A property that is initialized only when it is first accessed.
Explanation: In Swift, a lazy property is a property that is not initialized until it is first accessed. This can be useful for properties that are expensive to initialize or for properties that may not be needed during the lifetime of the object.
12. What is a computed property in Swift?
a. A property that is initialized with a default value.
b. A property that is initialized when it is first accessed.
c. A property that is computed based on the value of one or more other properties.
d. A property that is never accessed or used.
Ans: c. A property that is computed based on the value of one or more other properties.
Explanation: In Swift, a computed property is a property that is not backed by a stored value but instead computes its value on the fly based on the value of one or more other properties. Computed properties can be useful for encapsulating complex logic or for exposing a simplified view of an object’s state.
13. What is an optional in Swift?
a. A variable that can’t be changed once it is set.
b. A variable that can be nil or have a value of its type.
c. A variable that can only be set to a value of its type.
d. A variable that can’t be accessed or used.
Ans: b. A variable that can be nil or have a value of its type.
Explanation: In Swift, an optional is a variable that can either have a value of its type or be nil, which means it has no value. Optionals are often used to handle situations where a value might not be available or might not have been set yet.
14. What is a closure in Swift?
a. A way to define a function that can be passed as an argument to another function.
b. A way to define a type that can have a limited number of values.
c. A way to group multiple values into a single compound value.
d. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
Ans: d. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
Explanation: In Swift, a closure is a way to define a function that can capture and store references to any constants and variables from the context in which it is defined. Closures are often used to encapsulate functionality that can be passed around as a value, such as in completion handlers or when working with asynchronous code.
15. What is a protocol in Swift?
a. A way to define a set of methods and properties that a type must implement.
b. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
c. A way to define a type that can have a limited number of values.
d. A way to define a property that can have a default value.
Ans: a. A way to define a set of methods and properties that a type must implement.
Explanation: In Swift, a protocol is a way to define a set of methods and properties that a type must implement. Protocols are often used to define a contract between different types, allowing them to work together in a standardized way.
16. What is a type alias in Swift?
a. A way to define a new name for an existing type.
b. A way to define a new type that inherits from an existing type.
c. A way to define a new type that has the same interface as an existing type.
d. A way to define a new type that is a composite of two or more existing types.
Ans: a. A way to define a new name for an existing type.
Explanation: In Swift, a type alias is a way to define a new name for an existing type. Type aliases can be useful for making complex type names more readable or for providing alternate names for existing types.
17. What is a guard-let statement in Swift?
a. A way to define a conditional statement that executes if a condition is true and unwraps an optional.
b. A way to define a loop that continues until a certain condition is met.
c. A way to define a block of code that is executed if an error is thrown.
d. A way to define a switch statement that handles multiple cases at once.
Ans: a. A way to define a conditional statement that executes if a condition is true and unwraps an optional.
Explanation: In Swift, a guard-let statement is a conditional statement that is used to safely unwrap an optional value and execute a block of code if the optional value is not nil. The guard-let statement is often used to handle error conditions and to gracefully exit from a function or method if a required value is missing.
18. What is a lazy property in Swift?
a. A property that can only be set once and can’t be changed afterwards.
b. A property that is only initialized when it is accessed for the first time.
c. A property that is computed based on the value of one or more other properties.
d. A property that is never accessed or used.
Ans: b. A property that is only initialized when it is accessed for the first time.
Explanation: In Swift, a lazy property is a property that is only initialized when it is accessed for the first time. Lazy properties are often used to defer initialization of expensive or complex objects until they are actually needed.
19. What is a tuple in Swift?
a. A way to define a set of methods and properties that a type must implement.
b. A way to group multiple values into a single compound value.
c. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
d. A way to define a new name for an existing type.
Ans: b. A way to group multiple values into a single compound value.
Explanation: In Swift, a tuple is a way to group multiple values into a single compound value. Tuples are often used to return multiple values from a function or to pass multiple values as a single argument.
20. What is an extension in Swift?
a. A way to define a new type that inherits from an existing type.
b. A way to define a new type that is a composite of two or more existing types.
c. A way to define a set of methods and properties that can be added to an existing type.
d. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
Ans: c. A way to define a set of methods and properties that can be added to an existing type.
Explanation: In Swift, an extension is a way to add new functionality to an existing type, such as a class, struct, or enum. Extensions are often used to add methods, computed properties, and convenience initializers to existing types.
21. What is a didSet observer in Swift?
a. A way to observe changes to a property after it has been set.
b. A way to observe changes to a property before it is set.
c. A way to observe changes to a property as it is being set.
d. A way to observe changes to a variable that is never set.
Ans: a. A way to observe changes to a property after it has been set.
Explanation: In Swift, a didSet observer is a property observer that is called after a property has been set. The didSet observer can be used to perform additional actions or validation after a property has been set.
22. What is an @escaping closure in Swift?
a. A closure that captures and stores references to any constants and variables from the context in which it is defined.
b. A closure that can be passed as an argument to another function and executed asynchronously.
c. A closure that is guaranteed to execute immediately when it is called.
d. A closure that is only executed if a certain condition is met.
Ans: b. A closure that can be passed as an argument to another function and executed asynchronously.
Explanation: In Swift, an @escaping closure is a closure that can be passed as an argument to another function and executed asynchronously. The @escaping keyword is used to indicate that the closure will escape the current function scope and may be executed at a later time.
23. What is the difference between a class and a struct in Swift?
a. A class is a reference type and a struct is a value type.
b. A class can have inheritance and a struct cannot.
c. A class can have deinitializers and a struct cannot.
d. All of the above.
Ans: d. All of the above.
Explanation: In Swift, a class is a reference type and a struct is a value type. A class can have inheritance and deinitializers, while a struct cannot. These differences make classes and structs useful for different purposes in a program.
24. What is an optional in Swift?
a. A type that can only be used with certain functions and methods.
b. A type that represents a value that may or may not be present.
c. A type that can only be used with classes and not with structs.
d. A type that is used to represent a list of items.
Ans: b. A type that represents a value that may or may not be present.
Explanation: In Swift, an optional is a type that represents a value that may or may not be present. Optional values are often used when working with APIs or data sources that may not always provide a value for a particular property or parameter.
25. What is a closure in Swift?
a. A way to define a set of methods and properties that a type must implement.
b. A way to define a new type that is a composite of two or more existing types.
c. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
d. A way to define a new name for an existing type.
Ans: c. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
Explanation: In Swift, a closure is a way to define a function that can capture and store references to any constants and variables from the context in which it is defined. Closures are often used to pass functions as arguments to other functions, to define completion handlers, or to create asynchronous code.
26. What is a guard statement in Swift?
a. A way to define a conditional statement that executes if a condition is true and unwraps an optional.
b. A way to define a block of code that is executed if an error is thrown.
c. A way to define a switch statement that handles multiple cases at once.
d. A way to define a loop that executes a block of code while a certain condition is met.
Ans: a. A way to define a conditional statement that executes if a condition is true and unwraps an optional.
Explanation: In Swift, a guard statement is a conditional statement that is used to safely unwrap an optional value and execute a block of code if the optional value is not nil. The guard statement is often used to handle error conditions and to gracefully exit from a function or method if a required value is missing.
27. What is a protocol in Swift?
a. A way to define a set of methods and properties that a type must implement.
b. A way to define a new type that is a composite of two or more existing types.
c. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
d. A way to define a new name for an existing type.
Ans: a. A way to define a set of methods and properties that a type must implement.
Explanation: In Swift, a protocol is a way to define a set of methods and properties that a type must implement. Protocols are often used to define a common interface that multiple types can conform to, allowing for greater flexibility and code reuse.
28. What is an extension in Swift?
a. A way to add new functionality to an existing type.
b. A way to define a new type that is a composite of two or more existing types.
c. A way to define a function that can capture and store references to any constants and variables from the context in which it is defined.
d. A way to define a new name for an existing type.
Ans: a. A way to add new functionality to an existing type.
Explanation: In Swift, an extension is a way to add new functionality to an existing type. Extensions can add new methods, properties, and subscripts to a type, or modify existing ones. Extensions are often used to add convenience methods to existing types or to adapt existing types to work with new APIs.
29. What is a computed property in Swift?
a. A property that stores a value.
b. A property that is computed from other properties or methods.
c. A property that can only be accessed from within the same class.
d. A property that is automatically initialized when an instance is created.
Ans: b. A property that is computed from other properties or methods.
Explanation: In Swift, a computed property is a property that is not backed by a stored value, but is instead computed from other properties or methods. Computed properties are often used to provide a convenient way to access or calculate a value based on other properties or state within an object.
30. What is the difference between a weak and a strong reference in Swift?
a. A weak reference does not keep a reference count of an object, while a strong reference does.
b. A weak reference can be nil, while a strong reference cannot.
c. A weak reference is used to avoid retain cycles, while a strong reference is used to keep an object alive.
d. All of the above.
Ans: d. All of the above.
Explanation: In Swift, a weak reference is a reference to an object that does not keep a reference count of the object, and can be set to nil if the object is deallocated. Weak references are often used to avoid retain cycles, which can lead to memory leaks. A strong reference, on the other hand, keeps a reference count of the object and keeps it alive as long as the reference is held. Strong references are used to keep an object alive as long as it is needed.
The Swift MCQs and answers with explanations offer a helpful resource for the one who is seeking to enhance their knowledge and proficiency in using Swift for application development. Follow us @ freshersnow.com, for more learnings.