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interface Gettable<T> {
get() T
}
struct Animal<T> {
metadata T
}
fn (a Animal<T>) get<T>() T {
return a.metadata
}
// different struct implementing the same interface:
struct Mineral<T> {
value T
}
fn (m Mineral<T>) get<T>() T {
return m.value
}
////
fn extract<T>(xs []Gettable<T>) []T {
return xs.map(it.get())
}
fn extract_basic<T>(xs Gettable<T>) T {
return xs.get()
}
fn test_extract() {
a := Animal<int>{123}
b := Animal<int>{456}
c := Mineral<int>{789}
arr := [Gettable<int>(a), Gettable<int>(b), Gettable<int>(c)]
assert typeof(arr).name == '[]Gettable<int>'
x := extract<int>(arr)
assert x == [123, 456, 789]
}
// fn test_extract_multiple_instance_types() {
// a := Animal<string>{'123'}
// b := Animal<string>{'456'}
// c := Mineral<string>{'789'}
// arr := [Gettable<string>(a), Gettable<string>(b), Gettable<string>(c)]
// assert typeof(arr).name == '[]Gettable<string>'
// x := extract<string>(arr)
// assert x == ['123', '456', '789']
// }
fn test_extract_basic() {
a := Animal<int>{123}
b := Animal<int>{456}
c := Mineral<int>{789}
aa := extract_basic(a)
bb := extract_basic(b)
cc := extract_basic(c)
assert '$aa | $bb | $cc' == '123 | 456 | 789'
}
//////
interface Iterator<T> {
next() ?T
}
struct NumberIterator<T> {
limit T
mut:
val T
}
fn (mut i NumberIterator<T>) next<T>() ?T {
if i.val >= i.limit {
return none
}
i.val++
return i.val
}
fn test_iterator_implementation() {
mut i := Iterator<int>(NumberIterator<int>{
limit: 10
})
for {
if val := i.next() {
println(val)
} else {
println('iterator is done')
break
}
}
}
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