Swift .mapValues()

In Swift, the .mapValues() method transforms the values of a dictionary while keeping the keys unchanged. This method is part of the Dictionary structure and is useful for modifying or mapping only the values without altering the keys. This method returns a new dictionary with the same keys but with values transformed based on the provided closure, leaving the original dictionary unmodified.

Syntax

dictionaryName.mapValues ({ transform })

• dictionaryName: The instance of a Dictionary whose values are to be transformed.
• transformation: A closure that defines how each value in the dictionary should be transformed.

Example

In the following example, the mapValues() method is used to increase each student’s grade by 10 points while keeping the keys unchanged in the studentGrades dictionary:

var studentGrades = ["Jon": 65, "Nic": 77, "Mary": 80]

// Increase each student's grade by 10 points
let updatedGrades = studentGrades.mapValues { grade in
    grade + 10
}

print(updatedGrades)

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The output for the above code is:

["Jon": 75, "Nic": 87, "Mary": 90]

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In this example, mapValues() increases each grade by 10 points, while the keys ("Jon", "Nic", and "Mary") remain unchanged.