Batching Swift Arrays

arrayBatch.swift

extension Array {

    func elementsInRange(start: Int, length: Int) -> Slice<T>? {

        if start >= self.count {
            return nil
        }
        
        var lastIndex = start + length
        if start + length > self.count {
            lastIndex  = self.count
        }
        
        if lastIndex == start {
            return nil
        }

        return self[ start ..< lastIndex ]
    }
    
    func enumerateBatchesOfSize(size: Int, block: (Slice<T>)->()) {
        var startIndex: Int = 0

        while let sub = self.elementsInRange(startIndex, length: size) {
            block(sub)
            startIndex += size
        }
    }
    
}