core: Add godoc examples for LoadModule

context.go

@@ -124,7 +124,9 @@ func (ctx *Context) OnCancel(f func()) {
 // and store them on the same struct. Storing them on the same struct makes for
 // easy garbage collection when your host module is no longer needed.
 //
-// Loaded modules have already been provisioned and validated.
+// Loaded modules have already been provisioned and validated. Upon returning
+// successfully, this method clears the json.RawMessage(s) in the field since
+// the raw JSON is no longer needed, and this allows the GC to free up memory.
 func (ctx Context) LoadModule(structPointer interface{}, fieldName string) (interface{}, error) {
 	val := reflect.ValueOf(structPointer).Elem().FieldByName(fieldName)
 	typ := val.Type()

context_test.go

@@ -0,0 +1,118 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddy
+
+import (
+	"encoding/json"
+	"io"
+)
+
+func ExampleContext_LoadModule() {
+	// this whole first part is just setting up for the example;
+	// note the struct tags - very important; we specify inline_key
+	// because that is the only way to know the module name
+	var ctx Context
+	myStruct := &struct {
+		// This godoc comment will appear in module documentation.
+		GuestModuleRaw json.RawMessage `json:"guest_module,omitempty" caddy:"namespace=example inline_key=name"`
+
+		// this is where the decoded module will be stored; in this
+		// example, we pretend we need an io.Writer but it can be
+		// any interface type that is useful to you
+		guestModule io.Writer
+	}{
+		GuestModuleRaw: json.RawMessage(`{"name":"module_name","foo":"bar"}`),
+	}
+
+	// if a guest module is provided, we can load it easily
+	if myStruct.GuestModuleRaw != nil {
+		mod, err := ctx.LoadModule(myStruct, "GuestModuleRaw")
+		if err != nil {
+			// you'd want to actually handle the error here
+			// return fmt.Errorf("loading guest module: %v", err)
+		}
+		// mod contains the loaded and provisioned module,
+		// it is now ready for us to use
+		myStruct.guestModule = mod.(io.Writer)
+	}
+
+	// use myStruct.guestModule from now on
+}
+
+func ExampleContext_LoadModule_array() {
+	// this whole first part is just setting up for the example;
+	// note the struct tags - very important; we specify inline_key
+	// because that is the only way to know the module name
+	var ctx Context
+	myStruct := &struct {
+		// This godoc comment will appear in module documentation.
+		GuestModulesRaw []json.RawMessage `json:"guest_modules,omitempty" caddy:"namespace=example inline_key=name"`
+
+		// this is where the decoded module will be stored; in this
+		// example, we pretend we need an io.Writer but it can be
+		// any interface type that is useful to you
+		guestModules []io.Writer
+	}{
+		GuestModulesRaw: []json.RawMessage{
+			json.RawMessage(`{"name":"module1_name","foo":"bar1"}`),
+			json.RawMessage(`{"name":"module2_name","foo":"bar2"}`),
+		},
+	}
+
+	// since our input is []json.RawMessage, the output will be []interface{}
+	mods, err := ctx.LoadModule(myStruct, "GuestModulesRaw")
+	if err != nil {
+		// you'd want to actually handle the error here
+		// return fmt.Errorf("loading guest modules: %v", err)
+	}
+	for _, mod := range mods.([]interface{}) {
+		myStruct.guestModules = append(myStruct.guestModules, mod.(io.Writer))
+	}
+
+	// use myStruct.guestModules from now on
+}
+
+func ExampleContext_LoadModule_map() {
+	// this whole first part is just setting up for the example;
+	// note the struct tags - very important; we don't specify
+	// inline_key because the map key is the module name
+	var ctx Context
+	myStruct := &struct {
+		// This godoc comment will appear in module documentation.
+		GuestModulesRaw ModuleMap `json:"guest_modules,omitempty" caddy:"namespace=example"`
+
+		// this is where the decoded module will be stored; in this
+		// example, we pretend we need an io.Writer but it can be
+		// any interface type that is useful to you
+		guestModules map[string]io.Writer
+	}{
+		GuestModulesRaw: ModuleMap{
+			"module1_name": json.RawMessage(`{"foo":"bar1"}`),
+			"module2_name": json.RawMessage(`{"foo":"bar2"}`),
+		},
+	}
+
+	// since our input is map[string]json.RawMessage, the output will be map[string]interface{}
+	mods, err := ctx.LoadModule(myStruct, "GuestModulesRaw")
+	if err != nil {
+		// you'd want to actually handle the error here
+		// return fmt.Errorf("loading guest modules: %v", err)
+	}
+	for modName, mod := range mods.(map[string]interface{}) {
+		myStruct.guestModules[modName] = mod.(io.Writer)
+	}
+
+	// use myStruct.guestModules from now on
+}