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Checking all array elements match a condition: allSatisfy()

Paul Hudson       @twostraws

If you have a collection of objects and want to check that all of them match a specific condition, you should use the allSatisfy() method.

For example, if we had an array of words and wanted to make sure they all start with the letter “S”, we could write code like this:

let sWords = ["Swift", "Seahorse", "Solar"]
let allMatch = sWords.allSatisfy { $0.hasPrefix("S") }

Alternatively, if we had an array of exam results like this:

let scores = [85, 88, 95, 92]

We could decide whether that student passed their course by checking whether all their exam results were 85 or higher:

let passed = scores.allSatisfy { $0 >= 85 }

Available from iOS 8.0

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