Conditional Array Merge in Swift-CodePudding

Using SwiftUI 3.0 and Swift 5.5 on Xcode 13.2, target development > iOS 15.0.0

I'm trying to merge two arrays if a condition is met, but only one if it isn't.

I have come up with this simple function:

func conditionalArrayMerge(primaryArray: [Item], secondaryArray: [Item], condition: Bool) -> [Item] {
        if condition {
            return primaryArray   secondaryArray
        } else {
            return primaryArray
        }
    }

Is this the most efficient way to do this?

I don't want to do it like this

return condition ? primaryArray   secondaryArray : primaryArray

I tried doing it like so:

return primaryArray   { condition ? secondaryArray : [] } as [Item]

But obviously, it didn't work (unless it's not obvious?)

What's the most efficient way to return an array with conditional merges?

Thank you!

CodePudding user response：

Your syntax is wrong, you need parentheses around your ternary expression, not {}.

return primaryArray   (condition ? secondaryArray : [])

CodePudding user response：

What you're looking for is a variant of reduce that is missing from the standard library.

condition.reduce(primaryArray) { $0   secondaryArray }

public extension Bool {
  /// Modify a value if `true`.
  /// - Returns: An unmodified value, when false.
  @inlinable func reduce<Result>(
    _ resultWhenFalse: Result,
    _ makeResult: (_ resultWhenFalse: Result) throws -> Result
  ) rethrows -> Result {
    self
      ? try makeResult(resultWhenFalse)
      : resultWhenFalse
  }
}