如何从这个承诺层蛋糕中返回布尔值？

我有一个控制器方法，它接受一个字符串参数，这样我就可以测试用户是否有能力。用户拥有许多角色，并且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，我就这样保留了。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，如果用户有权限，我需要返回布尔值的方法。每次都会返回 false。我是否不正确地设置了 userHasCapability 属性，或者我应该执行其他操作来返回该值？

原始类型（例如 bool、int、string 等）是复制的，而不是引用的。这意味着你回来了userHasCapability，并且立即返回值 false，设置userHasCapability在该承诺的范围内，并不意味着它会被退回。事实上它不会。

此外，真正的响应需要采用承诺的形式，无论谁调用它，都需要以这种形式使用它。

这是操作顺序，假设foo calls 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

    },
    ...
});

事实上，角色是一个承诺，这意味着任何尝试使用它的人都需要期待一个承诺的结果（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;
      });
    }
});