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44 lines
2.9 KiB
Go
44 lines
2.9 KiB
Go
// Copyright (c) 2023 IBM Corp.
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// All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// 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
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package di implements functions and data types supporting dependency injection patterns
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//
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// The fundamental building block is the concept of a [Dependency]. This describes the abstract concept of a function, service or value together with its type.
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// Examples for dependencies can be as simple as configuration values such as the API URL for a service, the current username, a [Dependency] could be the map
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// of the configuration environment, an http client or as complex as a service interface. Important is that a [Dependency] only defines the concept but
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// not the implementation.
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//
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// The implementation of a [Dependency] is called a [Provider], the dependency of an `API URL` could e.g. be realized by a provider that consults the environment to read the information
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// or a config file or simply hardcode it.
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// In many cases the implementation of a [Provider] depends in turn on other [Dependency] (but never directly on other [Provider]s), a provider for an `API URL` that reads
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// the information from the environment would e.g. depend on a [Dependency] that represents this environment.
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//
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// It is the resposibility of the [InjectableFactory] to create an instance of a [Dependency]. All instances are considered singletons. Create an [InjectableFactory] via the [MakeInjector] method. Use [Resolve] to create a strongly typed
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// factory for a particular [InjectionToken].
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//
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// In most cases it is not required to use [InjectableFactory] directly, instead you would create a [Provider] via the [MakeProvider2] method (suffix indicates the number of dependencies). In this call
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// you give a number of (strongly typed) [Dependency] identifiers and a (strongly typed) factory function for the implementation. The dependency injection framework makes
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// sure to resolve the dependencies before calling the factory method.
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//
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// For convenience purposes it can be helpful to attach a default implementation of a [Dependency]. In this case use the [MakeTokenWithDefault2] method (suffix indicates the number of dependencies)
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// to define the [InjectionToken].
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//
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// [Provider]: [github.com/IBM/fp-go/di/erasure.Provider]
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// [InjectableFactory]: [github.com/IBM/fp-go/di/erasure.InjectableFactory]
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// [MakeInjector]: [github.com/IBM/fp-go/di/erasure.MakeInjector]
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package di
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//go:generate go run .. di --count 15 --filename gen.go
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