// Chain is the helper function for composing middlewares
// in specific order
func (wares Middlewares) Chain() endpoint.Middleware {
// if no middleware, return an passthrought middleware
if wares.Len() == 0 {
return func(inner endpoint.Endpoint) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
return inner(ctx, request)
}
}
}
// sort the middlewares
slice := wares.Slice()
return endpoint.Chain(slice[0], slice[1:]...)
}
func ExampleChain() {
e := endpoint.Chain(
annotate("first"),
annotate("second"),
annotate("third"),
)(myEndpoint)
if _, err := e(ctx, req); err != nil {
panic(err)
}
// Output:
// first pre
// second pre
// third pre
// my endpoint!
// third post
// second post
// first post
}