Returns the first index where the specified value appears in the collection.
SDK
- Xcode 10.0+
Framework
- Swift Standard Library
Declaration
func firstIndex(of element: Key) -> Dictionary<Key, Value>.Index?
Available when Element conforms to Equatable.
Parameters
elementAn element to search for in the collection.
Return Value
The first index where element is found. If element is not found in the collection, returns nil.
Discussion
After using first to find the position of a particular element in a collection, you can use it to access the element by subscripting. This example shows how you can modify one of the names in an array of students.
var students = ["Ben", "Ivy", "Jordell", "Maxime"]
if let i = students.firstIndex(of: "Maxime") {
students[i] = "Max"
}
print(students)
// Prints "["Ben", "Ivy", "Jordell", "Max"]"
Complexity: O(n), where n is the length of the collection.