What is an inout parameter

• Value is passed into the function, it is then modified by the function and is passed back out of the function to replace the original value.
• Pass-by-value-and-copy-back NOT pass-by-reference.
• Every inout parameter needs a & prefix.
• Must pass in a variable.
• If you pass in an UnsafeMutablePointer as a parameter but now we are passing by reference. Not recommended to use this if possible.

func increment(value: inout Int) {
  value += 1
}

var value = 0
increment(value: &value)

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