Angular.JS学习之依赖注入$injector详析

var FN_ARGS = /^function\s*[^\(]*\(\s*([^\)]*)\)/m;
var FN_ARG_SPLIT = /,/;
 // 获取服务名
var FN_ARG = /^\s*(_?)(\S ?)\1\s*$/;
var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
var $injectorMinErr = minErr('$injector');

function anonFn(fn) {
 // For anonymous functions, showing at the very least the function signature can help in
 // debugging.
 var fnText = fn.toString().replace(STRIP_COMMENTS, ''),
  args = fnText.match(FN_ARGS);
 if (args) {
 return 'function('   (args[1] || '').replace(/[\s\r\n] /, ' ')   ')';
 }
 return 'fn';
}

function annotate(fn, strictDi, name) {
 var $inject,
  fnText,
  argDecl,
  last;

 if (typeof fn === 'function') {
 if (!($inject = fn.$inject)) {
  $inject = [];
  if (fn.length) {
  if (strictDi) {
   if (!isString(name) || !name) {
   name = fn.name || anonFn(fn);
   }
   throw $injectorMinErr('strictdi',
   '{0} is not using explicit annotation and cannot be invoked in strict mode', name);
  }
  fnText = fn.toString().replace(STRIP_COMMENTS, '');
  argDecl = fnText.match(FN_ARGS);
  forEach(argDecl[1].split(FN_ARG_SPLIT), function(arg) {
   arg.replace(FN_ARG, function(all, underscore, name) {
   $inject.push(name);
   });
  });
  }
  fn.$inject = $inject;
 }
 } else if (isArray(fn)) {
 last = fn.length - 1;
 assertArgFn(fn[last], 'fn');
 $inject = fn.slice(0, last);
 } else {
 assertArgFn(fn, 'fn', true);
 }
 return $inject;
}

function createInternalInjector(cache, factory) {
 // 对服务注入器 providerInjector而言，只根据服务名获取服务，factory会抛出异常
 function getService(serviceName, caller) {
  if (cache.hasOwnProperty(serviceName)) {
  if (cache[serviceName] === INSTANTIATING) {
   throw $injectorMinErr('cdep', 'Circular dependency found: {0}',
     serviceName   ' <- '   path.join(' <- '));
  }
  return cache[serviceName];
  } else {
  try {
   path.unshift(serviceName);
   cache[serviceName] = INSTANTIATING;
   return cache[serviceName] = factory(serviceName, caller);
  } catch (err) {
   if (cache[serviceName] === INSTANTIATING) {
   delete cache[serviceName];
   }
   throw err;
  } finally {
   path.shift();
  }
  }
 }

 function invoke(fn, self, locals, serviceName) {
  if (typeof locals === 'string') {
  serviceName = locals;
  locals = null;
  }

  var args = [],
   // 解析并获取注入服务列表
   $inject = annotate(fn, strictDi, serviceName),
   length, i,
   key;

  for (i = 0, length = $inject.length; i < length; i  ) {
  key = $inject[i];
  if (typeof key !== 'string') {
   throw $injectorMinErr('itkn',
     'Incorrect injection token! Expected service name as string, got {0}', key);
  }
  // 注入的服务作为参数传入
  args.push(
   locals && locals.hasOwnProperty(key)
   ? locals[key]
   : getService(key, serviceName)
  );
  }
  if (isArray(fn)) {
  fn = fn[length];
  }

  // http://jsperf.com/angularjs-invoke-apply-vs-switch
  // #5388
  return fn.apply(self, args);
 }

 function instantiate(Type, locals, serviceName) {
  // Check if Type is annotated and use just the given function at n-1 as parameter
  // e.g. someModule.factory('greeter', ['$window', function(renamed$window) {}]);
  // Object creation: http://jsperf.com/create-constructor/2
  var instance = Object.create((isArray(Type) ? Type[Type.length - 1] : Type).prototype);
  var returnedValue = invoke(Type, instance, locals, serviceName);

  return isObject(returnedValue) || isFunction(returnedValue) ? returnedValue : instance;
 }

 return {
  invoke: invoke,
  instantiate: instantiate,
  get: getService,
  annotate: annotate,
  has: function(name) {
  return providerCache.hasOwnProperty(name   providerSuffix) || cache.hasOwnProperty(name);
  }
 };
 }

instanceInjector = (instanceCache.$injector =
   createInternalInjector(instanceCache, function
(serviceName, caller) { var provider = providerInjector.get(serviceName   providerSuffix, caller); return
 instanceInjector.invoke(provider.$get, provider, undefined, serviceName);
   }));

function provider(name, provider_) {
 assertNotHasOwnProperty(name, 'service');
 if (isFunction(provider_) || isArray(provider_)) {
  provider_ = providerInjector.instantiate(provider_);
 }
 if (!provider_.$get) {
  throw $injectorMinErr('pget', "Provider '{0}' must define $get factory method.", name);
 }
 return providerCache[name   providerSuffix] = provider_;
 }

 function enforceReturnValue(name, factory) {
 return function enforcedReturnValue() {
  var result = instanceInjector.invoke(factory, this);
  if (isUndefined(result)) {
  throw $injectorMinErr('undef', "Provider '{0}' must return a value from $get factory method.", name);
  }
  return result;
 };
 }

 function factory(name, factoryFn, enforce) {
 return provider(name, {
  $get: enforce !== false ? enforceReturnValue(name, factoryFn) : factoryFn
 });
 }

 function service(name, constructor) {
 return factory(name, ['$injector', function($injector) {
  return $injector.instantiate(constructor);
 }]);
 }

 function value(name, val) { return factory(name, valueFn(val), false); }

 function constant(name, value) {
 assertNotHasOwnProperty(name, 'constant');
 providerCache[name] = value;
 instanceCache[name] = value;
 }
 // 在服务实例化之后进行调用（拦截），拦截函数中注入实例化的服务，可以修改，扩展替换服务。
 function decorator(serviceName, decorFn) {
 var origProvider = providerInjector.get(serviceName   providerSuffix),
  orig$get = origProvider.$get;

 origProvider.$get = function() {
  var origInstance = instanceInjector.invoke(orig$get, origProvider);
  return instanceInjector.invoke(decorFn, null, {$delegate: origInstance});
 };
 }

angular.module("app",[])
  .provider("locationService",function(){
  ...
 })
 .controller("WeatherController",function($scope,locationService,$location){
  locationService.getWeather()
   .then(function(data){
    $scope.weather = data;
   },function(e){
    console.log("error message: "  e.message)
   });
 })