87 lines
3.0 KiB
Go
87 lines
3.0 KiB
Go
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/*******************************************************************************
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* Copyright 2019 Dell Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*******************************************************************************/
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package di
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import "sync"
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type Get func(serviceName string) interface{}
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// ServiceConstructor defines the contract for a function/closure to create a service.
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type ServiceConstructor func(get Get) interface{}
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// ServiceConstructorMap maps a service name to a function/closure to create that service.
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type ServiceConstructorMap map[string]ServiceConstructor
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// service is an internal structure used to track a specific service's constructor and constructed instance.
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type service struct {
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constructor ServiceConstructor
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instance interface{}
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}
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var GContainer *Container
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// Container is a receiver that maintains a list of services, their constructors, and their constructed instances in a
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// thread-safe manner.
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type Container struct {
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serviceMap map[string]service
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mutex sync.RWMutex
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}
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// NewContainer is a factory method that returns an initialized Container receiver struct.
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func NewContainer(serviceConstructors ServiceConstructorMap) *Container {
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c := Container{
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serviceMap: map[string]service{},
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mutex: sync.RWMutex{},
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}
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if serviceConstructors != nil {
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c.Update(serviceConstructors)
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}
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return &c
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}
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// Set updates its internal serviceMap with the contents of the provided ServiceConstructorMap.
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func (c *Container) Update(serviceConstructors ServiceConstructorMap) {
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c.mutex.Lock()
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defer c.mutex.Unlock()
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for serviceName, constructor := range serviceConstructors {
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c.serviceMap[serviceName] = service{
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constructor: constructor,
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instance: nil,
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}
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}
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}
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// get looks up the requested serviceName and, if it exists, returns a constructed instance. If the requested service
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// does not exist, it returns nil. Get wraps instance construction in a singleton; the implementation assumes an instance,
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// once constructed, will be reused and returned for all subsequent get(serviceName) calls.
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func (c *Container) get(serviceName string) interface{} {
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service, ok := c.serviceMap[serviceName]
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if !ok {
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// Returning nil allows the DIC to be queried for a object and not panic if it doesn't exist.
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return nil
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}
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if service.instance == nil {
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service.instance = service.constructor(c.get)
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c.serviceMap[serviceName] = service
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}
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return service.instance
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}
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// Get wraps get to make it thread-safe.
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func (c *Container) Get(serviceName string) interface{} {
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c.mutex.Lock()
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defer c.mutex.Unlock()
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return c.get(serviceName)
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}
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