/
node.go
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/
node.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package dig
import (
"fmt"
"reflect"
"github.com/pkg/errors"
)
type graphNode interface {
// Return value of the object
value(g *Graph) (reflect.Value, error)
// Other things that need to be present before this object can be created
dependencies() []interface{}
// unique identification per node
//
// TODO(glib): GFM-396
// consider using a custom type to identify objects, rather than a string
// type id struct { reflect.Type, string name, } or something of the sort
id() string
}
type node struct {
objType reflect.Type
cached bool
cachedValue reflect.Value
}
func (n node) id() string {
// in the future, more than just the type of node is going to be required
// for instance, when multiple types are allowed with different names
//
// TODO(glib): GFM-396
// Type.String() is not guaranteed to be unique and can return the same value
// for structs with the same name in a different package.
return n.objType.String()
}
type objNode struct {
node
obj interface{}
}
// Return the earlier provided instance
func (n *objNode) value(g *Graph) (reflect.Value, error) {
return reflect.ValueOf(n.obj), nil
}
func (n objNode) dependencies() []interface{} {
return nil
}
func (n objNode) String() string {
return fmt.Sprintf(
"(object) obj: %v, deps: nil, cached: %v, cachedValue: %v",
n.objType,
n.cached,
n.cachedValue,
)
}
type funcNode struct {
node
// constructor must be a function that returns the result type and an
// error
constructor interface{}
deps []interface{}
}
// Call the function and return the result
func (n *funcNode) value(g *Graph) (reflect.Value, error) {
if n.cached {
return n.cachedValue, nil
}
ct := reflect.TypeOf(n.constructor)
// check that all the dependencies have nodes present in the graph
// doesn't mean everything will go smoothly during resolve, but it
// drastically increases the chances that we're not missing something
for _, node := range g.nodes {
for _, dep := range node.dependencies() {
// check that the dependency is a registered objNode
if _, ok := g.nodes[dep]; !ok {
err := fmt.Errorf("%v dependency of type %v is not registered", ct, dep)
return reflect.Zero(ct), err
}
}
}
args := make([]reflect.Value, ct.NumIn(), ct.NumIn())
for idx := range args {
arg := ct.In(idx)
if node, ok := g.nodes[arg]; ok {
v, err := node.value(g)
if err != nil {
return reflect.Zero(n.objType), errors.Wrapf(err, "unable to resolve %v", arg)
}
args[idx] = v
}
}
cv := reflect.ValueOf(n.constructor)
values := cv.Call(args)
v := values[0]
// If the function has two return values, the second one is an error.
var err error
if len(values) > 1 {
err, _ = values[1].Interface().(error)
}
n.cached = true
n.cachedValue = v
return v, err
}
func (n funcNode) dependencies() []interface{} {
return n.deps
}
func (n funcNode) String() string {
return fmt.Sprintf(
"(function) id: %s, deps: %v, type: %v, constructor: %v, cached: %v, cachedValue: %v",
n.id(), n.deps, n.objType, n.constructor, n.cached, n.cachedValue,
)
}