详解Angular 4.x Injector

// angular2/packages/core/src/di/injector.tsexport abstract class Injector { static THROW_IF_NOT_FOUND = _THROW_IF_NOT_FOUND; static NULL: Injector = new _NullInjector(); /** * 用于根据给定的Token从注入器中获取相应的对象。 * 如果没有找到相应的对象，将返回notFoundValue设置的值。若notFoundValue的值与 * _THROW_IF_NOT_FOUND相等，则会抛出异常。 */ abstract get<T>(token: Type<T>|InjectionToken<T>, notFoundValue?: T): T;}const _THROW_IF_NOT_FOUND = new Object();

// angular2/packages/core/src/di/injector.tsclass _NullInjector implements Injector { get(token: any, notFoundValue: any = _THROW_IF_NOT_FOUND): any { if (notFoundValue === _THROW_IF_NOT_FOUND) {  throw new Error(`No provider for ${stringify(token)}!`); } return notFoundValue; }}

@Injectable()class Engine {}@Injectable()class Car { constructor(public engine:Engine) {}}var injector = ReflectiveInjector.resolveAndCreate([Car, Engine]);var car = injector.get(Car);expect(car instanceof Car).toBe(true);expect(car.engine instanceof Engine).toBe(true);

static resolveAndCreate(providers: Provider[], parent?: Injector): ReflectiveInjector { const ResolvedReflectiveProviders = ReflectiveInjector.resolve(providers); return ReflectiveInjector.fromResolvedProviders(ResolvedReflectiveProviders, parent);}

static resolve(providers: Provider[]): ResolvedReflectiveProvider[] { return resolveReflectiveProviders(providers);}

@Injectable()class Engine {}@Injectable()class Car { constructor(public engine:Engine) {}}var providers = ReflectiveInjector.resolve([Car, [[Engine]]]);expect(providers.length).toEqual(2);expect(providers[0] instanceof ResolvedReflectiveProvider).toBe(true);expect(providers[0].key.displayName).toBe("Car");expect(providers[1].key.displayName).toBe("Engine");

export type Provider = TypeProvider | ValueProvider | ClassProvider | ExistingProvider | FactoryProvider | any[];// ApiServiceexport interface TypeProvider extends Type<any> {}// { provide: ApiService, useClass: ApiService } export interface ClassProvider { // 用于设置与依赖对象关联的Token值，Token值可能是Type、InjectionToken、OpaqueToken的实例或字符串 provide: any;  useClass: Type<any>; // 用于标识是否multiple providers，若是multiple类型，则返回与Token关联的依赖对象列表 multi?: boolean; } // { provide: 'API_URL', useValue: 'http://my.api.com/v1' }export interface ValueProvider { provide: any; useValue: any; multi?: boolean;} // { provide: 'ApiServiceAlias', useExisting: ApiService } export interface ExistingProvider { provide: any; useExisting: any; multi?: boolean;} // { provide: APP_INITIALIZER, useFactory: configFactory, deps: [AppConfig], multi: true }export interface FactoryProvider { provide: any; useFactory: Function; deps?: any[]; // 用于设置工厂函数的依赖对象 multi?: boolean;}

export interface ResolvedReflectiveProvider { // 唯一的对象用来从ReflectiveInjector中获取对象 key: ReflectiveKey; // 工厂函数用于创建key相关的依赖对象  resolvedFactories: ResolvedReflectiveFactory[]; // 标识当前的provider是否为multi-provider multiProvider: boolean;}

export class ResolvedReflectiveFactory { constructor(  public factory: Function,  public dependencies: ReflectiveDependency[]) {}}

export class ReflectiveDependency { constructor(  public key: ReflectiveKey,   public optional: boolean,   public visibility: Self|SkipSelf|null) {} static fromKey(key: ReflectiveKey): ReflectiveDependency { return new ReflectiveDependency(key, false, null); }}

export class ReflectiveKey { constructor(public token: Object, public id: number) { if (!token) {  throw new Error('Token must be defined!'); } }  // 返回序列化的token get displayName(): string { return stringify(this.token); } // 获取token对应的ReflectiveKey static get(token: Object): ReflectiveKey { return _globalKeyRegistry.get(resolveForwardRef(token)); } // 获取系统中已注册ReflectiveKey的个数 static get numberOfKeys(): number { return _globalKeyRegistry.numberOfKeys; }}const _globalKeyRegistry = new KeyRegistry(); // 创建Key仓库export class KeyRegistry { private _allKeys = new Map<Object, ReflectiveKey>(); /** * 若token是ReflectiveKey类的实例，则直接返回。若_allKeys对象中包含token属性 * 则返回token对应的ReflectiveKey对象。否则创建一个新的ReflectiveKey对象，并 * 保存到_allKeys对象中 */ get(token: Object): ReflectiveKey { if (token instanceof ReflectiveKey) return token; if (this._allKeys.has(token)) {  return this._allKeys.get(token) !; } const newKey = new ReflectiveKey(token, ReflectiveKey.numberOfKeys); this._allKeys.set(token, newKey); return newKey; } // 获取已保存ReflectiveKey的个数 get numberOfKeys(): number { return this._allKeys.size; }}

export function resolveReflectiveProviders(providers: Provider[]) : ResolvedReflectiveProvider[] {  const normalized = _normalizeProviders(providers, []); // 步骤一  const resolved = normalized.map(resolveReflectiveProvider); // 步骤二  const resolvedProviderMap = mergeResolvedReflectiveProviders(resolved, new Map()); // 步骤三  return Array.from(resolvedProviderMap.values()); // 步骤四}

const normalized = _normalizeProviders(providers, []);// 规范化Providersfunction _normalizeProviders(providers: Provider[], res: Provider[]): Provider[] { providers.forEach(b => {  // providers: [Type] => providers: [{provide: Type, useClass: Type }]  if (b instanceof Type) {    res.push({provide: b, useClass: b});  } else if (b && typeof b == 'object' && (b as any).provide !== undefined) {   res.push(b as NormalizedProvider);  } else if (b instanceof Array) { // 若b是数组，则递归调用_normalizeProviders()方法   _normalizeProviders(b, res);  } else {   throw invalidProviderError(b);  } }); return res;}interface NormalizedProvider extends TypeProvider, ValueProvider, ClassProvider,   ExistingProvider, FactoryProvider {}

const resolved = normalized.map(resolveReflectiveProvider);// 解析NormalizedProvider为ResolvedReflectiveProviderfunction resolveReflectiveProvider(provider: NormalizedProvider): ResolvedReflectiveProvider { return new ResolvedReflectiveProvider_(   ReflectiveKey.get(provider.provide), [resolveReflectiveFactory(provider)],   provider.multi || false);}// 用于创建已解析的Provider实例export class ResolvedReflectiveProvider_ implements ResolvedReflectiveProvider { constructor(   public key: ReflectiveKey,    public resolvedFactories: ResolvedReflectiveFactory[],   public multiProvider: boolean) {} get resolvedFactory(): ResolvedReflectiveFactory { return this.resolvedFactories[0]; }}// 解析NormalizedProvider对象，创建ResolvedReflectiveFactory对象function resolveReflectiveFactory(provider: NormalizedProvider): ResolvedReflectiveFactory { let factoryFn: Function; let resolvedDeps: ReflectiveDependency[]; if (provider.useClass) {  // { provide: ApiService, useClass: ApiService }   const useClass = resolveForwardRef(provider.useClass);  factoryFn = reflector.factory(useClass);  resolvedDeps = _dependenciesFor(useClass); } else if (provider.useExisting) {  // { provide: 'ApiServiceAlias', useExisting: ApiService }   factoryFn = (aliasInstance: any) => aliasInstance;  resolvedDeps = [ReflectiveDependency.fromKey(ReflectiveKey.get(provider.useExisting))]; } else if (provider.useFactory) {  // { provide: APP_INITIALIZER, useFactory: configFactory, deps: [AppConfig],   //   multi: true }  factoryFn = provider.useFactory;  resolvedDeps = constructDependencies(provider.useFactory, provider.deps); } else {  // { provide: 'API_URL', useValue: 'http://my.api.com/v1' }  factoryFn = () => provider.useValue;  // const _EMPTY_LIST: any[] = [];  resolvedDeps = _EMPTY_LIST; } return new ResolvedReflectiveFactory(factoryFn, resolvedDeps);}

const resolvedProviderMap = mergeResolvedReflectiveProviders(resolved, new Map());export function mergeResolvedReflectiveProviders(  providers: ResolvedReflectiveProvider[],  normalizedProvidersMap: Map<number, ResolvedReflectiveProvider>):  Map<number, ResolvedReflectiveProvider> {  for (let i = 0; i < providers.length; i++) {  const provider = providers[i];   // 从normalizedProvidersMap对象中获取key.id对应的ResolvedReflectiveProvider对象  const existing = normalizedProvidersMap.get(provider.key.id);  if (existing) {    // 如果当前的provider不是multi provider，则抛出异常   if (provider.multiProvider !== existing.multiProvider) {    throw mixingMultiProvidersWithRegularProvidersError(existing, provider);   }   // 如果当前的provider是multi provider，则把当前provider的resolvedFactories   // 列表中的每一项添加到已存在的provider对象的resolvedFactories列表中。   if (provider.multiProvider) {    for (let j = 0; j < provider.resolvedFactories.length; j++) {     existing.resolvedFactories.push(provider.resolvedFactories[j]);    }   } else {     // 如果当前的provider不是multi provider，则覆盖已存在的provider    normalizedProvidersMap.set(provider.key.id, provider);   }  } else {   let resolvedProvider: ResolvedReflectiveProvider;   // 如果当前的provider是multi provider，则创建一个新的ResolvedReflectiveProvider对象   if (provider.multiProvider) {    resolvedProvider = new ResolvedReflectiveProvider_(      provider.key, provider.resolvedFactories.slice(), provider.multiProvider);   } else {    resolvedProvider = provider;   }   // 在normalizedProvidersMap中保存已解析的ResolvedReflectiveProvider对象   normalizedProvidersMap.set(provider.key.id, resolvedProvider);  } } return normalizedProvidersMap;}

// resolvedProviderMap的values，创建ResolvedReflectiveProvider[]Array.from(resolvedProviderMap.values());/** * 基于一个类似数组或可迭代对象创建一个新的数组实例 *  * arrayLike：转换成真实数组的类数组对象或可遍历对象。 * mapFn(可选)：如果指定了该参数，则最后生成的数组会经过该函数的加工处理后再返回。 * thisArg(可选)：执行mapFn函数时this的值。 */Array.from(arrayLike[, mapFn[, thisArg]])

static fromResolvedProviders(providers: ResolvedReflectiveProvider[], parent?: Injector): ReflectiveInjector {  return new ReflectiveInjector_(providers, parent);}

@Injectable()class Engine {}@Injectable()class Car { constructor(public engine:Engine) {}}var providers = ReflectiveInjector.resolve([Car, Engine]);var injector = ReflectiveInjector.fromResolvedProviders(providers);expect(injector.get(Car) instanceof Car).toBe(true);

// 构造次数_constructionCounter: number = 0;// ResolvedReflectiveProvider列表 public _providers: ResolvedReflectiveProvider[];// 父级注入器 public _parent: Injector|null;// ReflectiveKey id列表 keyIds: number[];// 依赖对象列表 objs: any[];

export class ReflectiveInjector_ implements ReflectiveInjector { constructor(_providers: ResolvedReflectiveProvider[], _parent?: Injector) {   this._providers = _providers;   // 设置父级注入器   this._parent = _parent || null;   const len = _providers.length;   this.keyIds = new Array(len);   this.objs = new Array(len);   // 初始化keyIds列表和objs对象列表   for (let i = 0; i < len; i++) {    this.keyIds[i] = _providers[i].key.id;    this.objs[i] = UNDEFINED;   } }}const UNDEFINED = new Object();

// 基于Provider列表并创建子注入器resolveAndCreateChild(providers: Provider[]): ReflectiveInjector {  const ResolvedReflectiveProviders = ReflectiveInjector.resolve(providers);  return this.createChildFromResolved(ResolvedReflectiveProviders);}// 基于已解析的ResolvedReflectiveProvider列表，创建子注入器createChildFromResolved(providers: ResolvedReflectiveProvider[]): ReflectiveInjector {  const inj = new ReflectiveInjector_(providers);  inj._parent = this;  return inj;}

// 获取当前注入器的父级注入器get parent(): Injector|null { return this._parent; }// 获取token对应的依赖对象get(token: any, notFoundValue: any = THROW_IF_NOT_FOUND): any {  return this._getByKey(ReflectiveKey.get(token), null, notFoundValue);}// 根据ReflectiveKey及visibility可见性，获取对应的依赖对象private _getByKey(key: ReflectiveKey, visibility: Self|SkipSelf|null, notFoundValue: any): any {  // const INJECTOR_KEY = ReflectiveKey.get(Injector);   if (key === INJECTOR_KEY) {   return this;  }  // 判断该依赖对象是否使用@Self装饰器定义，表示从本级注入器获取依赖对象  if (visibility instanceof Self) {   return this._getByKeySelf(key, notFoundValue);  } else {   // 使用默认的方式获取依赖对象   return this._getByKeyDefault(key, notFoundValue, visibility);  }}// 从本级注入器获取依赖对象 _getByKeySelf(key: ReflectiveKey, notFoundValue: any): any {  const obj = this._getObjByKeyId(key.id);  return (obj !== UNDEFINED) ? obj : this._throwOrNull(key, notFoundValue);}// 使用默认的方式获取依赖对象_getByKeyDefault(key: ReflectiveKey, notFoundValue: any,   visibility: Self|SkipSelf|null): any {  let inj: Injector|null;  // 判断该依赖对象是否使用@SkipSelf装饰器定义，表示不从本级注入器获取依赖对象  if (visibility instanceof SkipSelf) {   inj = this._parent;  } else {   inj = this;  }  // 从本级注入器获取依赖对象，若本级获取不到，则从父级注入器中查找  while (inj instanceof ReflectiveInjector_) {   const inj_ = <ReflectiveInjector_>inj;   const obj = inj_._getObjByKeyId(key.id);   if (obj !== UNDEFINED) return obj;   inj = inj_._parent;  }  if (inj !== null) {   return inj.get(key.token, notFoundValue);  } else {   return this._throwOrNull(key, notFoundValue);  }}// 获取keyId对应的对象，如依赖对象未创建，则调用_new()方法创建一个，然后保存到// this.objs对象列表中private _getObjByKeyId(keyId: number): any {  for (let i = 0; i < this.keyIds.length; i++) {   if (this.keyIds[i] === keyId) {    // const UNDEFINED = new Object();    if (this.objs[i] === UNDEFINED) {     this.objs[i] = this._new(this._providers[i]);    }    return this.objs[i];   }  }  return UNDEFINED;}

// 创建依赖对象_new(provider: ResolvedReflectiveProvider): any {  // 判断是否存在循环依赖  if (this._constructionCounter++ > this._getMaxNumberOfObjects()) {   throw cyclicDependencyError(this, provider.key);  }  return this._instantiateProvider(provider);}// 获取最大的对象个数private _getMaxNumberOfObjects(): number { return this.objs.length; }// 根据已解析的provider创建依赖对象。若是multi provider则，循环创建multi provider对象。 private _instantiateProvider(provider: ResolvedReflectiveProvider): any {  if (provider.multiProvider) {   const res = new Array(provider.resolvedFactories.length);   for (let i = 0; i < provider.resolvedFactories.length; ++i) {    res[i] = this._instantiate(provider, provider.resolvedFactories[i]);   }   return res;  } else {   return this._instantiate(provider, provider.resolvedFactories[0]);  }}// 根据已解析的provider和已解析的工厂创建依赖对象private _instantiate(   provider: ResolvedReflectiveProvider,   ResolvedReflectiveFactory: ResolvedReflectiveFactory): any {  // 获取对象工厂函数  const factory = ResolvedReflectiveFactory.factory;  // 获取工厂函数所依赖的对象列表  let deps: any[];  try {   deps = ResolvedReflectiveFactory.dependencies       .map(dep => this._getByReflectiveDependency(dep));  } catch (e) {   if (e.addKey) {    e.addKey(this, provider.key);   }   throw e;  }  // 调用对象工厂函数创建依赖对象  let obj: any;  try {   obj = factory(...deps);  } catch (e) {   throw instantiationError(this, e, e.stack, provider.key);  }  return obj; }

// 若通过@Optional装饰器定义该依赖对象，表示该依赖对象是可选的，当获取不到时返回null。private _getByReflectiveDependency(dep: ReflectiveDependency): any {  return this._getByKey(dep.key, dep.visibility, dep.optional ? null : THROW_IF_NOT_FOUND);}