Ioc dev

go-kid/ioc Development Guide

Comprehensive guide for developing applications with the go-kid/ioc dependency injection framework.

Requires Go 1.21+

---

⚠️ 核心约束（必读）

在使用 go-kid/ioc 时，必须遵守以下规则，违反会导致注入失败或运行时错误：

1. 依赖注入字段必须导出（首字母大写）

// ❌ 错误 - 小写字段会被忽略
type Service struct {
    repo *Repository `wire:""`  // 不会被注入！
}

// ✅ 正确 - 首字母大写
type Service struct {
    Repo *Repository `wire:""`  // 会被正确注入
}

2. 配置注入必须使用专用机制

❌ 禁止直接访问 configure 对象：

// ❌ 错误 - 不要直接注入或访问 configure
type Service struct {
    Configure configure.Configure `wire:""` // 错误！
}

func (s *Service) Init() {
    // ❌ 错误 - 不要直接调用 configure.Get()
    host := s.Configure.Get("db.host")
}

✅ 必须使用以下方式之一：

// 方式 1: 使用 prop/value/prefix tag
type Service struct {
    Host string    `prop:"db.host"`           // ✅ 单个配置值
    Port int       `value:"${db.port:3306}"`  // ✅ 带默认值
    DB   *DBConfig `prefix:"database"`        // ✅ 绑定配置树
}

// 方式 2: 实现 ConfigurationProperties 接口
type DBConfig struct {
    Host string `yaml:"host"`
    Port int    `yaml:"port"`
}
func (c *DBConfig) Prefix() string { return "database" }

// 方式 3: 构造函数参数（自动绑定）
func NewService(cfg *DBConfig) *Service {  // cfg 会自动从配置加载
    return &Service{host: cfg.Host}
}

3. 组件注册必须是指针

// ❌ 错误
ioc.Register(MyService{})

// ✅ 正确
ioc.Register(&MyService{})

---

Quick Start

1. Register Components & Start App

import "github.com/go-kid/ioc"

// Register components
ioc.Register(&MyService{}, &Repository{})

// Start application
app, err := ioc.Run()
if err != nil {
    panic(err)
}
defer app.Close()

2. Inject Dependencies

type MyService struct {
    Repo   *Repository `wire:""`           // inject by type
    Logger Logger      `wire:""`           // inject interface
    Config *AppConfig  `prefix:"app"`      // bind config
    Port   int         `prop:"server.port:8080"` // config value with default
}

3. Constructor Injection

func NewService(repo *Repository, cfg *DBConfig) *Service {
    return &Service{repo: repo, cfg: cfg}
}

ioc.Register(NewService, &Repository{})
ioc.Run(app.SetConfig("config.yaml"))

---

Topic Guide

This skill covers three core areas. For detailed information, consult the reference documents:

📦 Component Injection

When to use: Registering components, dependency wiring, selecting implementations

Quick reference:

• Register: ioc.Register(&MyComp{}) or ioc.Provide[T](constructor)
• Inject by type: Svc *Service \wire:""``
• Inject by name: Svc *Service \wire:"my-service"``
• Inject all: Svcs []Service \wire:""``
• Inject by method: Comp *MyComp \func:"MethodName"``
• Primary selection: Embed definition.WirePrimaryComponent
• Qualifier: wire:",qualifier=groupA"
• Optional: wire:",required=false"
• Scope: Implement ScopeComponent → ScopeSingleton / ScopePrototype

📖 Full documentation: references/component-injection.md

⚙️ Configuration Injection

When to use: Loading config files, binding config values, placeholders, expressions

Quick reference:

• Load config: app.SetConfig("config.yaml")
• Bind struct: DB *DBConfig \prefix:"database"``
• Config value: Host string \prop:"server.host"``
• Placeholder: DSN string \value:"${db.dsn}"``
• Default value: Port int \value:"${port:8080}"``
• Expression: Sum int \value:"#{1+2}"``
• Mixed: Total int \value:"#{${price} * ${qty}}"``
• ConfigurationProperties: Implement Prefix() string

📖 Full documentation: references/config-injection.md

🔄 Application Lifecycle

When to use: App startup, initialization order, lifecycle hooks, shutdown, events

Quick reference:

• Start app: ioc.Run(options...)
• With context: ioc.RunWithContext(ctx, options...)
• After properties set: Implement AfterPropertiesSet() error
• Init hook: Implement Init() error
• Run after startup: Implement ApplicationRunner → Run() error
• Graceful shutdown: Implement Close() error
• Execution order: Implement Order() int
• Lazy init: Embed definition.LazyInitComponent
• Conditional: Implement Condition(ctx ConditionContext) bool
• Events: Implement ApplicationEventListener

📖 Full documentation: references/lifecycle.md

---

Common Patterns

Pattern 1: Service with Config & Dependencies

type UserService struct {
    Repo   *UserRepository `wire:""`
    Cache  *Redis          `wire:""`
    Config *ServiceConfig  `prefix:"user-service"`
}

func (s *UserService) Init() error {
    // Initialize after dependencies injected
    return s.Cache.Connect(s.Config.RedisURL)
}

Pattern 2: Constructor with Type-Safe Registration

func NewUserService(repo *UserRepository, cfg *ServiceConfig) *UserService {
    return &UserService{repo: repo, config: cfg}
}

// Type-safe: panics if return type doesn't match
ioc.Provide[UserService](NewUserService)

Pattern 3: Multiple Implementations with Qualifier

// Mark implementations
type MySQLRepo struct{}
func (r *MySQLRepo) Qualifier() string { return "mysql" }

type PostgresRepo struct{}
func (r *PostgresRepo) Qualifier() string { return "postgres" }

// Select by qualifier
type App struct {
    MySQL    Repository   `wire:",qualifier=mysql"`
    Postgres Repository   `wire:",qualifier=postgres"`
    AllRepos []Repository `wire:""` // gets both
}

Pattern 4: Graceful Startup & Shutdown

type HTTPServer struct {
    Port   int    `prop:"server.port:8080"`
    server *http.Server
}

func (s *HTTPServer) Run() error {
    s.server = &http.Server{Addr: fmt.Sprintf(":%d", s.Port)}
    return s.server.ListenAndServe()
}

func (s *HTTPServer) Close() error {
    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()
    return s.server.Shutdown(ctx)
}

---

Startup Flow Overview

ioc.Run(options...)
  1. Apply SettingOptions + global settings
  2. Load configuration (loaders → binder)
  3. Scan component definitions
  4. Resolve dependencies & create components
  5. Inject dependencies (wire, value, prop, prefix tags)
  6. Call lifecycle hooks (AfterPropertiesSet → Init)
  7. Execute ApplicationRunners (in Order)
  8. Publish ApplicationStartedEvent

---

Important Gotchas

参见文档开头的 ⚠️ 核心约束 了解必须遵守的规则

1. Components must be pointers: ioc.Register(&MyService{}) not MyService{}
2. Exported fields only: wire:"" tags on unexported fields are ignored
3. Config injection only via tags: Never inject configure.Configure directly; use value/prop/prefix tags or ConfigurationProperties
4. Required by default: Use required=false to make injection optional
5. Circular refs: Supported for singletons via early exposure, NOT for prototypes
6. Order matters: PostProcessors run in defined order (see lifecycle docs)
7. prop vs value: prop:"key" equals value:"${key}"

---

Configuration

When you need detailed information on a specific topic, read the corresponding reference file. The main topics are:

• Component wiring & injection → references/component-injection.md
• Config loading & binding → references/config-injection.md
• App lifecycle & startup → references/lifecycle.md

For debugging and troubleshooting, use the ioc-debug skill. For testing and extensions, use the ioc-test skill.