无法建立这种可观察

Question

要建立一个完整的User实体，我需要执行此任务：从userId

1. 得到一个UserResponse（REST API响应）从userId
得到一个 List<Role>
2. 获取从UserResponse.addressId
3. 一个Address构建从UserResponse的User和List<Role>和Address。

我尝试这样做：

public Observable<User> getUserById(String userId) {  
    return Observable.zip(getUserResponse(userId), getRoles(userId), new Func2<UserResponse, List<Role>, User>() { 
     @Override 
     public User call(UserResponse response, List<Role> roles) { 
      //I need the address here! 
     } 
}); 

但我不知道如何使用AddressRepository来从UserResponse.addressId的Address。

public interface AddressRepository { 
    Observable<Address> getAddress(String addressId); 
} 

的User构造是这样的：

public User(String userId, Address address, List<Role> roles) { ... } 

我希望你能理解。很难解释这个问题。

Answer 1

使用cache()操作：

public Observable<User> getUserById(String userId) { 
    Observable<UserResponse> response = getUserResponse(userId).cache(); 
    return Observable.zip(
    response, 
    response.flatMap(new Func1<UserResponse, Observable<Address>>() { 
     @Override 
     public Observable<Address> call(UserResponse resp) { 
      return addressRepository.getAddress(resp.addressId); 
     } 
    }), 
    getRoles(userId), new Func3<UserResponse, Address, List<Role>, User>() { 
     @Override 
     public User call(UserResponse resp, Address ad, List<Role> roles) { 
      //Now, I have all I need to build the User =) 
     } 
    } 
    }); 
} 

Answer 2

我找到了一个解决方案：

public Observable<User> getUserById(String userId) { 
    return Observable.zip(
     getUserResponse(userId), 
     getUserResponse(userId).flatMap(new Func1<UserResponse, Observable<Address>>() { 
      @Override 
      public Observable<Address> call(UserResponse resp) { 
       return addressRepository.getAddress(resp.addressId); 
      } 
     }), 
     getRoles(userId), new Func3<UserResponse, Address, List<Role>, User>() { 
      @Override 
      public User call(UserResponse resp, Address ad, List<Role> roles) { 
       //Now, I have all I need to build the User =) 
      } 
     } 
}); 

任何意见将不胜感激。 “重复”getUserResponse(userId)的呼叫是否是一种很好的做法？我没有找到解决这个问题的另一种方法。

Answer 3

getUserResponse(userId).publish.autoConnect(2); 

将使其ConnectableObservable只有开始出版哪里有2个用户，这样你会一次调用后端。

getUserAddress（）将调用getUserResponse并从中获取地址。

现在拉链getUserResponse，getUserAddress和getRoles（用户ID）一起:)

Answer 4

您可以使用flatMap一个变种这样做

public Observable<User> getUserById(String userId) { 
    return Observable.zip(
      getUserResponse(userId).flatMap(new Func1<UserResponse, Observable<Address>>() { 
      @Override 
      public Observable<Address> call(UserResponse resp) { 
       return addressRepository.getAddress(resp.addressId); 
      } 
      }, 
      new Func2<UserResponse, Address, Pair<UserResponse,Address>>() { 
      @Override 
      public Pair<UserResponse,Address> call(UserResponse resp, Address addr) { 
       return new Pair<UserResponse,Address>(resp,addressRepository.getAddress(resp.addressId)); 
      }  
      }), 
      getRoles(userId), 
      new Func2<Pair<UserResponse, Address>, List<Role>, User>(){ 
      @Override 
      public User call(UserResponse resp, Address ad, List<Role> roles) { 
      //Now, I have all I need to build the User 
      }    
      } 
     ); 
}