In-place collection element removal 관련

HACKING WITH SWIFT

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What's new in Swift?

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In-place collection element removal | Changes in Swift 4.2

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In-place collection element removal

Available from Swift 4.2

SE-0197 (apple/swift-evolution) introduced a new removeAll(where:) method that performs a high-performance, in-place filter for collections. You give it a closure condition to run, and it will strip out all objects that match the condition.

For example, if you have a collection of names and want to remove people called “Terry”, you’d use this:

var pythons = ["John", "Michael", "Graham", "Terry", "Eric", "Terry"]
pythons.removeAll { $0.hasPrefix("Terry") }
print(pythons)

Now, you might very well think that you could accomplish that by using filter() like this:

pythons = pythons.filter { !$0.hasPrefix("Terry") }

However, that doesn’t use memory very efficiently, it specifies what you don’t want rather than what you want, and more advanced in-place solutions come with a range of complexities that are off-putting to novices. Ben Cohen, the author of SE-0197, gave a talk at dotSwift 2018 where he discussed the implementation of this proposal in more detail – if you’re keen to learn why it’s so efficient, you should start there!

Other Changes in Swift 4.2

Derived collections of enum cases | Changes in Swift 4.2

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Derived collections of enum cases

Warning and error diagnostic directives | Changes in Swift 4.2

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Warning and error diagnostic directives

Dynamic member look up | Changes in Swift 4.2

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Dynamic member look up

Enhanced conditional conformances | Changes in Swift 4.2

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Enhanced conditional conformances

Random number generation and shuffling | Changes in Swift 4.2

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Random number generation and shuffling

Simpler, more secure hashing | Changes in Swift 4.2

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Simpler, more secure hashing

Checking sequence elements match a condition | Changes in Swift 4.2

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Checking sequence elements match a condition

Boolean toggling | Changes in Swift 4.2

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Boolean toggling

Download Swift 4.2 playground