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graph_inject.go
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graph_inject.go
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package inj
import (
"fmt"
"reflect"
)
// Given a function, call it with arguments from the graph.
// Throws a runtime error in the form of a panic on failure.
func (g *Graph) Inject(fn interface{}, args ...interface{}) {
// Reflect the input
f := reflect.ValueOf(fn)
// It's slightly faster to store the type rather than constantly
// retrieving it.
ftype := f.Type()
// We can only accept functions
if ftype.Kind() != reflect.Func {
panic("[inj.Inject] Passed argument is not a function")
}
// Variadic functions aren't currently supported
if ftype.IsVariadic() {
panic("[inj.Inject] Passed function is variadic")
}
// Assemble extra arg types list
xargs := make([]reflect.Type, len(args))
for i := 0; i < len(args); i++ {
xargs[i] = reflect.TypeOf(args[i])
}
// Number of required incoming arguments
argc := ftype.NumIn()
// Assemble a list of function arguments
argv := make([]reflect.Value, argc)
for i := 0; i < argc; i++ {
func() {
// Get an incoming arg reflection type
in := ftype.In(i)
// Look in the additional args list for the requirement
for j := 0; j < len(xargs); j++ {
if xargs[j].AssignableTo(in) {
argv[i] = reflect.ValueOf(args[j])
return
}
}
// Find an entry in the graph
for j := 0; j < len(g.indexes); j++ {
if g.indexes[j].AssignableTo(in) {
argv[i] = g.nodes[g.indexes[j]].Value
return
}
}
// If it's STILL not found, panic
panic(fmt.Sprintf("[inj.Inject] Can't find value for arg %d [%s]", i, in))
}()
}
// Make the function call, with the args which should now be complete.
f.Call(argv)
}