Swift Interview Questions and Answers Part 2

 

     How do you use the "inout" keyword in Swift?

• The "inout" keyword is used to indicate that a parameter passed to a function can be modified within the function and the changes will reflect outside the function. 
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• Inout allows you to pass a variable as an argument to a function and have the function change its value and it can also be used to pass values to a function as an inout parameter.
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• How do you use the "mutating" keyword in Swift?
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• The "mutating" keyword is used to indicate that a method can modify the properties of a struct or an enumeration. 
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• The mutating keyword is used on methods that change the internal state of a struct or an enumeration. Without the mutating keyword, structs and enums are treated as value types, meaning that their properties can't be modified.
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• How do you use the "required" keyword in Swift?
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• The "required" keyword is used to indicate that a class initializer must be implemented by all subclasses of that class. 
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• By marking an initializer as "required", you enforce that all subclasses must provide an implementation for that initializer. 
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• This ensures that all subclasses of a class are properly initialized, even if they don't have their own designated initializers.
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• How do you use the "private" keyword in Swift?
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• The "private" keyword is used to indicate that a property, method, or initializer should only be accessible from within the same source file in which it is defined. It is used to hide implementation details from other parts of the codebase, and to prevent external classes or structs from accessing or modifying the private members.
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• How do you use the "final" keyword in Swift?
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• The "final" keyword is used to indicate that a class, method, or property should not be overridden or subclassed. It is used to prevent subclasses from modifying the behavior of the class or method, and to ensure that the class or method will always behave in the same way.
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• How do you use the "override" keyword in Swift?
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• The "override" keyword is used to indicate that a subclass is providing a new implementation of a method, property, or subscript that it has inherited from a superclass. 
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• It is used to indicate that the subclass is overriding the implementation of the superclass, and to prevent accidental overrides of methods, properties or subscripts that are not intended to be overridden.
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• How do you use the "weak" keyword in Swift?
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• The "weak" keyword is used to indicate that a reference to an object should be weak. A weak reference is a reference that does not keep the object it refers to alive. It is used to prevent retain cycles in cases where two objects have a strong reference to each other.
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• How do you use the "static" keyword in Swift?
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• The "static" keyword is used to indicate that a property, method, or subscript belongs to the type itself, rather than to instances of that type. 
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• It allows you to access the property, method, or subscript without having to instantiate the class. Static properties, methods and subscripts can be accessed directly on the class, and are shared among all instances of that class.
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• How do you use the "optional binding" in Swift?
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• Optional binding is a way to check if an optional contains a value, and if it does, to assign that value to a non-optional variable.
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• The syntax for optional binding is "if let" or "guard let" statement followed by a variable name, an equal sign, and the optional variable to be checked. If the optional variable contains a value, the value is assigned to the non-optional variable, otherwise the code block does not execute.
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• How do you use the "switch" statement in Swift?
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• The "switch" statement is used to test multiple possible values of an expression. The syntax for a switch statement is "switch" followed by the expression to be tested, and one or more "case" statements. Each case statement contains a value or a pattern to match the expression and the code block to be executed if the value or pattern matches the expression.
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• How do you use the "default" case in a "switch" statement in Swift?
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• The "default" case in a "switch" statement is used to handle any values that do not match the cases specified in the "switch" statement. 
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• It is placed after all the other cases and is executed if none of the cases match the expression. 
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• The code block inside the default case will be executed if none of the other cases match the expression.
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• How do you use the "continue" statement in a loop in Swift?
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• The "continue" statement is used inside a loop to skip the current iteration and continue with the next iteration. It is used to skip over specific iterations of a loop, rather than exiting the loop altogether. 
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• The continue statement causes the loop to immediately move to the next iteration, skipping any remaining code in the current iteration.
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• How do you use the "break" statement in a loop in Swift?
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• The "break" statement is used inside a loop to exit the loop entirely. It is used to exit a loop early, before the loop's condition is met. The break statement causes the loop to exit immediately, and the program continues with the next line of code following the loop.
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• How do you use the "fallthrough" statement in a "switch" statement in Swift?
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• The "fallthrough" statement is used inside a "switch" statement to execute the code block of the next case. It is used to execute multiple cases in a switch statement, even if the case conditions are not met. The fallthrough statement causes the code execution to continue to the next case, regardless of whether the case's condition is met. It should be used with caution, as it can make the control flow of the switch statement unpredictable.
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• How do you use the "defer" statement in Swift?
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• The "defer" statement is used to execute a block of code before the program exits the current scope. 
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• It is useful for cleaning up resources, such as closing files or releasing memory, that should be done regardless of how the program exits the current scope. 
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• The defer statement guarantees that the code block will be executed, even if the program exits the scope due to an error.
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• How do you use the "assert" statement in Swift?
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• The "assert" statement is used to check for a condition and trigger a runtime error if the condition is not true. 
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• It is used to detect and handle programming errors during development, and can be used to check for invalid input, unexpected states, or other conditions that should not occur during normal operation of the program. 
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• The assert statement is removed from the compiled code in release builds, and should not be used for error handling in production code.
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• What is protocol oriented programming?
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• Protocol-oriented programming (POP) is a programming paradigm in Swift that emphasizes the use of protocols and protocol extensions to define the behavior and functionality of types. 
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• POP is based on the idea that protocols, rather than classes or structs, should be the primary building blocks of an application.
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• One of the key benefits of using POP is that it allows for more flexible and composable code, as well as the ability to add new functionality to existing types through protocol extensions. 
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• This makes the code more maintainable and less prone to errors, as well as more reusable across different parts of an application.

     What is Upcast and Downcast?

• Upcasting refers to the process of converting an object from a subclass to its superclass. This is also known as an "implicit cast" because the compiler can automatically perform the conversion. 
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• For example, if you have a class "Dog" that inherits from a class "Animal", upcasting would be converting a "Dog" object to an "Animal" object.
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• Downcasting refers to the process of converting an object from a superclass to its subclass. This is also known as an "explicit cast" because the developer must explicitly specify the desired type and the compiler checks if the conversion is valid.
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• For example, if you have a class "Animals" that is a superclass of "Dog", downcasting would be converting an "Animals" object to a "Dog" object.
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• It's important to note that if a downcast is attempted on an object that doesn't actually conform to the intended type, the program will fail to compile or will trigger a runtime error.
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• In swift, you can use "as?" or "as!" to downcast. "as?" will return an optional value, the downcast is successful it will return the downcasted object otherwise it will return nil, "as!" will force the downcast and if it fails, it will trigger a runtime error.

    Swift Interview Questions and Answers Part 1