Optional unwrapping by condition (filter?) in Swift

OptionalFilter.swift

extension Optional {
    // Will return the value of optional if it is not nil and if the function `condition` evaluates to true.
    // Otherwise, returns nil
    func filter(condition: T -> Bool) -> T? {
        if let x = self {
            if condition(x) {
                return x
            }
        }
        
        return nil
    }
}

// Usage
let x: Int? = 5
let y = x.filter{ $0 == 5 }



// in if let

// evaluate to true
if let z = x.filter({ $0 == 5 }) {
    // This code will execute. z will be set to 5.
}

if let z = x.filter({ value in value == 5 }) {
    // This code will execute. z will be set to 5.
} else {
    // This code will not execute
}

if let z = x.filter({ value in value != nil }) {
    // This code will execute. z will be set to 5.
} else {
    // This code will not execute
}

// evaluate to false
if let z = x.filter({ $0 == 7 }) {
    // This code will not execute
} else {
    // This code will execute since x is not equal to 7
}

if let z = x.filter({ $0 == nil }) {
    // This code will not execute
} else {
    // This code will execute since x is not equal to 7
}