Mutate structs in array

MutateStructArray.swift

struct Foo {
    var i: Int = 0
}

var arr = [Foo(), Foo()]
print(arr)

for var a in arr {
    a.i = 1
}
print(arr)


for (i, var a) in arr.enumerate() {
    a.i = 1
}
print(arr)


for i in arr.indices {
    arr[i].i = 1
}
print(arr)