In this post, we will implement enumerations in swift.
What’s an enumeration?
According to the official documentation of Swift:
“An enumeration defines a common type for a group of related values.”
In simple words, an enumeration is a user defined data type which stores a set of values. Examples of such sets can be days of the week, days of the month, etc.
How to define enums in swift?
In swift, the enumeration is defined using the following syntax:
enum EnumerationName { // cases }
Here enum is the keyword, and enumerationName is the name for the enumeration. The following example code creates an enum which stores days of the week.
enum DaysOfWeek{ case monday case tuesday case wednesday case thursday case friday case saturday case sunday }
Once the enums are created, we define a variable of this enum type as the following code shows:
var today = DaysOfWeek.tuesday
When we assign DaysOfWeek.tuesday to variable today, type of today becomes an enumeration. Switch statements which we studied in this post, can be used to match individual enumeration values.
today = .thursday switch today{ case .monday, .tuesday, .wednesday, .thursday, .friday: print("Working Days") case .saturday, .sunday: print("Holidays") }
After first initialization, we can assign values to the enum variables only using “.casename”, as done in the above example through “.thursday“.
The output of above program is “Working Days” as “.thursday” falls into the first switch case.
Raw Values
In swift, enumerations can be initialized with raw values. In this example, we assign “Int” to the enumeration, making sure all the cases in this enumeration will have an integer raw value by default on initialization.
enum DaysOfWeek: Int{ case monday case tuesday case wednesday case thursday case friday case saturday case sunday } var today = DaysOfWeek.thursday print("\(today.rawValue)")
When we fetch the raw value using “today.rawValue“, we get an output of three. Because by default, if we don’t assign values to all the cases, swift assigns “0” to the first case and the remaining cases are incremented by “1“, i.e. monday is 0, tuesday is 1, wednesday is 2, thursday is 3 and so on.
Similarly, if we assign monday with 61, the output of thursday will be 64. Here, Swift assigns 61 to monday and all other values are incremented by 1.
Last, we assign separate and different values to all the enumeration cases.
The type of raw values in the enumerations could be float or double or string also.
Associated Values
The raw values are of the same type, so all cases store values of the same type. But in swift, enumeration cases can also store values of different data types. These values associated with each enumeration case are called associated values. For example the below enumeration:
enum EmployeeRecord{ case name(String, String) case age(Int) case weight(Float) }
Here we have an enumeration EmployeeRecord with three cases(values): name which can store two string values, age which can store one integer value and weight which can store a float value.
The next question that arises is how to initialize a variable of this enumeration type?
var employee = EmployeeRecord.name("John", "Doe")
Consider the name case which stores two strings. While initializing the variable employee with the enumeration EmployeeRecord, we fill in the values of the associated strings with “John” and “Doe“.
switch employee { case .name(let first, let last): print("First Name: \(first)") print("Last Name: \(last)") case .age(var age): print("Age: \(age)") case .weight(let weight): print("Weight: \(weight)") default: print("Invalid value") }
Similarly, when we check these cases in the switch, we have to add the associated values as constants or variables to be able to use them. For the name, there are “let first” and “let second“.
With this, we complete enumeration in swift. If any questions, leave them in comments below. You can find the code for this post here.