74 lines
2.6 KiB
Go
74 lines
2.6 KiB
Go
// Copyright (c) 2019 Uber Technologies, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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package fx
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import (
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"fmt"
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"reflect"
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)
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// Populate sets targets with values from the dependency injection container
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// during application initialization. All targets must be pointers to the
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// values that must be populated. Pointers to structs that embed In are
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// supported, which can be used to populate multiple values in a struct.
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//
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// This is most helpful in unit tests: it lets tests leverage Fx's automatic
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// constructor wiring to build a few structs, but then extract those structs
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// for further testing.
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func Populate(targets ...interface{}) Option {
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// Validate all targets are non-nil pointers.
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targetTypes := make([]reflect.Type, len(targets))
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for i, t := range targets {
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if t == nil {
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return invokeErr(fmt.Errorf("failed to Populate: target %v is nil", i+1))
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}
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rt := reflect.TypeOf(t)
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if rt.Kind() != reflect.Ptr {
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return invokeErr(fmt.Errorf("failed to Populate: target %v is not a pointer type, got %T", i+1, t))
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}
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targetTypes[i] = reflect.TypeOf(t).Elem()
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}
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// Build a function that looks like:
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//
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// func(t1 T1, t2 T2, ...) {
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// *targets[0] = t1
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// *targets[1] = t2
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// [...]
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// }
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//
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fnType := reflect.FuncOf(targetTypes, nil, false /* variadic */)
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fn := reflect.MakeFunc(fnType, func(args []reflect.Value) []reflect.Value {
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for i, arg := range args {
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reflect.ValueOf(targets[i]).Elem().Set(arg)
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}
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return nil
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})
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return Invoke(fn.Interface())
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}
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func invokeErr(err error) Option {
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return Invoke(func() error {
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return err
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})
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}
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