Swift 2.1 how to create predicate

Question

The compiler is complaining about his piece of code and not sure how to fix:

NSProcessInfo.processInfo().environment.contains("UITESTING")

And it complains that it cannot convert value of type STring to expected argument type '@noescape((String, String)) throws -> Bool

I'm using Xcode 7.3.1 with Swift 2.2

Answer 1

NSProcessInfo.processInfo().environment returns a [String : String] dictionary.

To use contains on a dictionary you have to pass a closure, not a String.

Examples for Swift 2:

// This is just to make the answer easier to read
let env = NSProcessInfo.processInfo().environment

To test if the keys contain your String:

let result = env.contains { $0.0.containsString("UITESTING") }

or to test equality, for example:

let result = env.contains { $0.0 == "UITESTING" }

To test if the values contain your String:

let result = env.contains { $0.1.containsString("UITESTING") }

or equals:

let result = env.contains { $0.1 == "UITESTING" }

$0 is each item in the dictionary, .0 is the key and .1 is the value.

To understand better, here's the long form syntax:

let result = env.contains { (key, value) in key.containsString("UITESTING") }

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And in Swift 3, in case someone needs it:

let env = ProcessInfo.processInfo.environment
let result = env.contains { $0.key.contains("UITESTING") }
let result = env.contains { $0.value.contains("UITESTING") }
let result = env.contains { (key, value) in key.contains("UITESTING") }