Swift - Changing an array value of function call

Question

I like to change an array value for my function call.

Code for my ViewController2 that calls a function calculate

class ViewController2: UIViewController , UITableViewDelegate, UITableViewDataSource {

var springDisplacement : [Float] {return calculate(forceView2, stiffView2, springNumView2) }

}

Code for function calculate

public func calculateBoundary (f:[Float], s:[Float], n:NSInteger) -> (forceBound1:Float, forceBound2: Float, displacement:[Float]) {

    println("\nForces in the array are")
    for rows in 0...n{
        if(rows==0||rows==n)
        { f[rows] = 0.0 }                
            println(f[rows])          
        }
}

I have an error: '@lValue $T5' is not identical to 'Float', when i want to change my f[rows] = 0.0

Any advices?

Answer 1

This is because f parameter is an immutable array. You can change this to a mutable array parameter by using the function signature as follows

func calculateBoundary (var f:[Float], var s:[Float], n:NSInteger)  -> (forceBound1:Float, forceBound2: Float, displacement:[Float]) { // }

If you want to also modify the original arrays passed to the function, you need to use inout parameters.

func calculateBoundary (inout f:[Float],inout s:[Float], n:NSInteger) -> (forceBound1:Float, forceBound2: Float, displacement:[Float]) { // }

You can call it like this

var f : [Float] = [1.0,2.0]
var g : [Float] = [1.0,2.0]

let result = calculateBoundary(&f, &g, 1)

Answer 2

f array is not mutable. You need to pass the f array as inout parameter:

 func calculateBoundary (inout f:[Float], s:[Float], n:NSInteger) -> (forceBound1:Float, forceBound2: Float, displacement:[Float]) {...}

Then you can call calculateBoundary like this:

var springDisplacement : [Float] {return calculate(&forceView2, stiffView2, springNumView2) }