如何从这个承诺层蛋糕中返回布尔值？

Question

我有一个控制器方法，它接受一个字符串参数，所以我可以测试用户是否有能力。用户有许多角色，并且这些角色附加了一系列权限，我们需要检查它是否包含该功能。我知道这过于冗长，但为了理解起见，我已经离开了。稍后会重构...

App.WorkspaceIndexController = Ember.Controller.extend({
    userCan: function(capability) {
      var userHasCapability = false;
      var userPromise = this.get('session.user');

      var rolesPromise = userPromise.then( function(user) {
        return user.get('roles');
      });

      var filteredRolesPromise = rolesPromise.then(function (roles) {
        return roles.filter(function (role) {
          return role.get('workspace') === self.get('workspace');
        });
      });

      filteredRolesPromise.then(function (filteredRoles) {
        return filteredRoles.forEach(function (role) {
          userHasCapability = _.contains(_.flatten(role.get('permissions'), 'name'), capability);
        });
      });

      return userHasCapability;

    },
    ...
});

我遇到的问题是，如果用户拥有权限，我需要该方法返回布尔值。这每次都返回 false。我是否错误地设置了 userHasCapability 属性，或者我应该做些什么来返回值？

Answer 1

原始类型，如 bool、int、string 等是复制的，而不是引用的。这意味着您返回userHasCapability，并且立即返回值false，将userHasCapability设置在该promise的范围内，并不意味着它会被返回。事实上不会。

此外，真正的响应需要采用承诺的形式，并且任何调用它的人也需要以这种形式使用它。

这是操作顺序，假设foo 调用userCan。

App.WorkspaceIndexController = Ember.Controller.extend({
    foo: function(){
      var j = this.userCan('eat worms');  // 1. method is called, 6. j is set to false, we fall out of foo
    },
    userCan: function(capability) {
      var userHasCapability = false;
      var userPromise = this.get('session.user');

      var rolesPromise = userPromise.then( function(user) { // 2. promise built
        return user.get('roles'); // 7. this promise happens is resolved
      });

      var filteredRolesPromise = rolesPromise.then(function (roles) { // 3. another promise built
        return roles.filter(function (role) { //8 return the filter cause 7 resolved
          return role.get('workspace') === self.get('workspace');
        });
      });

      filteredRolesPromise.then(function (filteredRoles) { // 4. another promise built
        return filteredRoles.forEach(function (role) {  //9. 8 resolved so do this now, even though no one references userHasCapability anymore
          userHasCapability = _.contains(_.flatten(role.get('permissions'), 'name'),  capability);
        });
      });

      return userHasCapability; // 5. false is returned

    },
    ...
});

角色是一个承诺这一事实意味着任何尝试使用它的人都需要期待一个承诺作为结果（或者不要使用异步，也不要使用承诺）

App.WorkspaceIndexController = Ember.Controller.extend({
    foo: function(){
      this.userCan('eat worms').then(function(result){
        console.log(result);
      });
    },
    userCan: function(capability) {
      var userHasCapability = false;
      var userPromise = this.get('session.user');

      var rolesPromise = userPromise.then( function(user) { // 2. promise built
        return user.get('roles'); // 7. this promise happens is resolved
      });

      var filteredRolesPromise = rolesPromise.then(function (roles) { // 3. another promise built
        return roles.filter(function (role) { //8 return the filter cause 7 resolved
          return role.get('workspace') === self.get('workspace');
        });
      });

      return filteredRolesPromise.then(function (filteredRoles) { // 4. another promise built
        filteredRoles.forEach(function (role) {  //9. 8 resolved so do this now, even though no one references userHasCapability anymore
          userHasCapability = _.contains(_.flatten(role.get('permissions'), 'name'),  capability);
        });
        return userHasCapability;
      });
    }
});