首页 \ 问答 \ 避免结构中的PhantomData强制执行类型约束(Avoiding PhantomData in a struct to enforce type constraints)

避免结构中的PhantomData强制执行类型约束(Avoiding PhantomData in a struct to enforce type constraints)

 我正在尝试开发一种批处理系统。 在那里我想使用某种Process结构，它拥有所有与流程相关的部分。 当前的实现使用PhantomData来强制执行类型约束：  
pub struct Process<P: Producer<U>, T: Transformer<U, V>, C: Consumer<V>, U,V> 
{
    producer: P,
    transformer: T, 
    consumer: C,
    p1: PhantomData<U>,
    p2: PhantomData<V>,
}
 
 这个想法是由Producer发出的类型将被Transformer （可能是另一种类型）使用，并由Consumer 。 因此类型必须匹配。  
 Process结构应该拥有实现Producer ， Transformer和Consumer特性的项目。 我想这就是为什么我需要使用类型参数。 因为我不能直接使用这个特质  
...
producer: Producer<U>,
...
 
 因为编译时未知的大小。  
 有没有更好的方法来做到这一点？ 我对Rust很新，所以我可能会在错误的方向思考。  
 该解决方案有效，但对于那些PhantomData字段看起来有点奇怪。 也许这只是PhantomData的用途？ 

I'm trying to develop a kind of batch system. Within that I'd like to use some kind of Process struct, which owns all process related parts. The current implementation uses PhantomData to enforce the type constraints: 
pub struct Process<P: Producer<U>, T: Transformer<U, V>, C: Consumer<V>, U,V> 
{
    producer: P,
    transformer: T, 
    consumer: C,
    p1: PhantomData<U>,
    p2: PhantomData<V>,
}
 
The idea is that type emitted by the Producer will be used by the Transformer (maybe to a different type) and consumed by the Consumer. Therefore the types must match. 
The Process struct should own the items implementing the Producer, Transformer and Consumer traits. I think that's why I need to use type parameters. Since I cannot use the the trait directly like 
...
producer: Producer<U>,
...
 
because of the unknown size at compile time. 
Is there a better way of doing this? I'm pretty new to Rust, so I might be thinking in the wrong direction. 
The solution works, but it looks a bit odd with those PhantomData fields. Maybe that is just what PhantomData is used for?

原文：https://stackoverflow.com/questions/33409546

更新时间：2022-04-01 10:04

最满意答案

 我在片段的onCreateView中调用了SetValues方法。 最后我解决了这个问题  
 主要活动  
public class CameraDetails extends Activity {
    private CameraData camera = new CameraData();

    Fragment network = new NetworkFragment();
    Fragment remoteUser = new RemoteUserFragment();
    Fragment rtsp = new RTSPFragmentTab();
    Fragment video = new VideoFragmentTab();
    Fragment record = new RecordFragmentTab();
    Fragment alarm = new AlarmFragmentTab();
    Fragment productinfo = new ProductInfoFragmentTab();

    private G.Interface mNetworkInterface = null;
    private G.Interface mRemoteUserInterface = null;    

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.cameradetails);

        initCameraData();

        ActionBar actionBar = getActionBar();
        actionBar.setDisplayShowHomeEnabled(false);
        actionBar.setDisplayShowTitleEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // network tab
        ActionBar.Tab tab = actionBar.newTab();
        tab.setText("Network");
        tab.setIcon(R.drawable.ic_launcher);
        tab.setTabListener(new TabListener(network));
        actionBar.addTab(tab);

        // remote user tab
        tab = actionBar.newTab();
        tab.setText("Remote User");
        tab.setIcon(R.drawable.ic_launcher);
        tab.setTabListener(new TabListener(remoteUser));
        actionBar.addTab(tab);        
    }

    public void initCameraData(){
        try{
            byte[] by = new byte[512];
            String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
            File file = new File(extStorageDirectory, "dump.hex");
            BufferedInputStream in = new BufferedInputStream( new FileInputStream(file));
            in.read(by);
            in.close();
            camera.set( by );           
        } catch(Exception e){
            e.printStackTrace();
        }

    }

    public void onClick(View v){
        getActionBar().setSelectedNavigationItem(0);
        if(!mNetworkInterface.Validate())
            return;

        getActionBar().setSelectedNavigationItem(1);
        if(!mRemoteUserInterface.Validate())
            return;

        try{
            byte[] bytes = camera.get();
            String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
            File file = new File(extStorageDirectory, "dump.hex");
            BufferedOutputStream out = new BufferedOutputStream( new FileOutputStream(file, false));
            out.write(bytes);
            out.close();
            Log.v("Data", "Setup data updated");
        } catch (Exception e) {
            e.printStackTrace();
            return ;
        }
    }

    public CameraData getCameraData(){
        return camera;
    }

    public void setNetworkListener( G.Interface Interface ){
        this.mNetworkInterface = Interface;
    }

    public void setRemoteUserListener( G.Interface Interface ){
        this.mRemoteUserInterface = Interface;
    }

}
 
 网络碎片  
public class NetworkFragment extends Fragment implements G.Interface {
    View rootView;
    Activity mActivity;
    CameraData camera;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.network_layout, container, false);
        Log.i("NetworkFragment", "CreateView");
        SetValues();
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        mActivity = activity;
        ((CameraDetails)mActivity).setNetworkListener(this);
        camera = ((CameraDetails)mActivity).getCameraData();
        Log.i("NetworkFragment", "Activity Attached");
        super.onAttach(activity);
    }

    @Override
    public boolean Validate() {
        try {
            String s;
            int i;

            // ip address
            camera.mNetwork.IPAddress = G.GetIPText(rootView, R.id.cd_ip_address);
            if( camera.mNetwork.IPAddress.isEmpty()){
                Toast.makeText(mActivity, "Please enter a valid ip address", Toast.LENGTH_SHORT).show();
                return false;
            }

            // subnet mask
            camera.mNetwork.SubnetMask = G.GetIPText(rootView, R.id.cd_subnetmask);
            if( camera.mNetwork.SubnetMask.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid subnetmask", Toast.LENGTH_SHORT).show();
                return false;
            }


            // gateway
            camera.mNetwork.Gateway = G.GetIPText(rootView, R.id.cd_gateway);
            if( camera.mNetwork.Gateway.isEmpty()){
                Toast.makeText(mActivity, "Please enter a valid gateway", Toast.LENGTH_SHORT).show();
                return false;
            }

            // com port
            camera.mNetwork.CommPort = G.GetInteger(rootView, R.id.cd_comm_port);
            if( camera.mNetwork.CommPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid Communication Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // mimg port
            camera.mNetwork.MImgPort = G.GetInteger(rootView, R.id.cd_mimg_port);
            if( camera.mNetwork.MImgPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid MIMG Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // webserver port
            camera.mNetwork.WebServerPort = G.GetInteger(rootView, R.id.cd_web_server_port);
            if( camera.mNetwork.WebServerPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid webserver Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi id
            camera.mNetwork.WiFiId = G.GetText(rootView, R.id.cd_wifi_id);
            if( camera.mNetwork.WiFiId.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid WiFi Id", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi password
            camera.mNetwork.WiFiPassword = G.GetText(rootView, R.id.cd_wifi_pwd);
            if( camera.mNetwork.WiFiPassword.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid WiFi Password", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi mode
            camera.mNetwork.WiFiMode = (byte)G.GetSpinnerOptions(rootView, R.id.cd_wifi_mode);
            if( camera.mNetwork.WiFiMode == -1 ){
                Toast.makeText(mActivity, "Please select a valid wifi mode from list", Toast.LENGTH_SHORT).show();
                return false;
            }

            Log.i("NetworkFragment", "Validation OK");
        } catch( Exception e ){
            e.printStackTrace();
        }
        return true;
    }

    public void SetValues() {
        try {
            // ip address
            EditText et = (EditText)rootView.findViewById(R.id.cd_ip_address);
            et.setText(camera.mNetwork.IPAddress);

            // subnet mask
            et = (EditText)rootView.findViewById(R.id.cd_subnetmask);
            et.setText(camera.mNetwork.SubnetMask);

            // gateway
            et = (EditText)rootView.findViewById(R.id.cd_gateway);
            et.setText(camera.mNetwork.Gateway);

            // com port
            et = (EditText)rootView.findViewById(R.id.cd_comm_port);
            et.setText(""+camera.mNetwork.CommPort);

            // mimg port
            et = (EditText)rootView.findViewById(R.id.cd_mimg_port);
            et.setText(""+camera.mNetwork.MImgPort);

            // webserver port
            et = (EditText)rootView.findViewById(R.id.cd_web_server_port);
            et.setText(""+camera.mNetwork.WebServerPort);

            // wifi id
            et = (EditText)rootView.findViewById(R.id.cd_wifi_id);
            et.setText(camera.mNetwork.WiFiId);

            // wifi password
            et = (EditText)rootView.findViewById(R.id.cd_wifi_pwd);
            et.setText(camera.mNetwork.WiFiPassword);

            // wifi mode
            Spinner sp = (Spinner)rootView.findViewById(R.id.cd_wifi_mode);
            sp.setSelection(camera.mNetwork.WiFiMode, true);


            Log.i("NetworkFragment", "SetValues OK");

        } catch( Exception e ){
            e.printStackTrace();
        }
    }

}
 
 无论如何，感谢@ cricket_007帮助我理解片段标签操作 

I called SetValues method in onCreateView of the fragment. Finally i solved the problem 
Main Activity 
public class CameraDetails extends Activity {
    private CameraData camera = new CameraData();

    Fragment network = new NetworkFragment();
    Fragment remoteUser = new RemoteUserFragment();
    Fragment rtsp = new RTSPFragmentTab();
    Fragment video = new VideoFragmentTab();
    Fragment record = new RecordFragmentTab();
    Fragment alarm = new AlarmFragmentTab();
    Fragment productinfo = new ProductInfoFragmentTab();

    private G.Interface mNetworkInterface = null;
    private G.Interface mRemoteUserInterface = null;    

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.cameradetails);

        initCameraData();

        ActionBar actionBar = getActionBar();
        actionBar.setDisplayShowHomeEnabled(false);
        actionBar.setDisplayShowTitleEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // network tab
        ActionBar.Tab tab = actionBar.newTab();
        tab.setText("Network");
        tab.setIcon(R.drawable.ic_launcher);
        tab.setTabListener(new TabListener(network));
        actionBar.addTab(tab);

        // remote user tab
        tab = actionBar.newTab();
        tab.setText("Remote User");
        tab.setIcon(R.drawable.ic_launcher);
        tab.setTabListener(new TabListener(remoteUser));
        actionBar.addTab(tab);        
    }

    public void initCameraData(){
        try{
            byte[] by = new byte[512];
            String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
            File file = new File(extStorageDirectory, "dump.hex");
            BufferedInputStream in = new BufferedInputStream( new FileInputStream(file));
            in.read(by);
            in.close();
            camera.set( by );           
        } catch(Exception e){
            e.printStackTrace();
        }

    }

    public void onClick(View v){
        getActionBar().setSelectedNavigationItem(0);
        if(!mNetworkInterface.Validate())
            return;

        getActionBar().setSelectedNavigationItem(1);
        if(!mRemoteUserInterface.Validate())
            return;

        try{
            byte[] bytes = camera.get();
            String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
            File file = new File(extStorageDirectory, "dump.hex");
            BufferedOutputStream out = new BufferedOutputStream( new FileOutputStream(file, false));
            out.write(bytes);
            out.close();
            Log.v("Data", "Setup data updated");
        } catch (Exception e) {
            e.printStackTrace();
            return ;
        }
    }

    public CameraData getCameraData(){
        return camera;
    }

    public void setNetworkListener( G.Interface Interface ){
        this.mNetworkInterface = Interface;
    }

    public void setRemoteUserListener( G.Interface Interface ){
        this.mRemoteUserInterface = Interface;
    }

}
 
Network Fragment 
public class NetworkFragment extends Fragment implements G.Interface {
    View rootView;
    Activity mActivity;
    CameraData camera;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.network_layout, container, false);
        Log.i("NetworkFragment", "CreateView");
        SetValues();
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        mActivity = activity;
        ((CameraDetails)mActivity).setNetworkListener(this);
        camera = ((CameraDetails)mActivity).getCameraData();
        Log.i("NetworkFragment", "Activity Attached");
        super.onAttach(activity);
    }

    @Override
    public boolean Validate() {
        try {
            String s;
            int i;

            // ip address
            camera.mNetwork.IPAddress = G.GetIPText(rootView, R.id.cd_ip_address);
            if( camera.mNetwork.IPAddress.isEmpty()){
                Toast.makeText(mActivity, "Please enter a valid ip address", Toast.LENGTH_SHORT).show();
                return false;
            }

            // subnet mask
            camera.mNetwork.SubnetMask = G.GetIPText(rootView, R.id.cd_subnetmask);
            if( camera.mNetwork.SubnetMask.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid subnetmask", Toast.LENGTH_SHORT).show();
                return false;
            }


            // gateway
            camera.mNetwork.Gateway = G.GetIPText(rootView, R.id.cd_gateway);
            if( camera.mNetwork.Gateway.isEmpty()){
                Toast.makeText(mActivity, "Please enter a valid gateway", Toast.LENGTH_SHORT).show();
                return false;
            }

            // com port
            camera.mNetwork.CommPort = G.GetInteger(rootView, R.id.cd_comm_port);
            if( camera.mNetwork.CommPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid Communication Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // mimg port
            camera.mNetwork.MImgPort = G.GetInteger(rootView, R.id.cd_mimg_port);
            if( camera.mNetwork.MImgPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid MIMG Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // webserver port
            camera.mNetwork.WebServerPort = G.GetInteger(rootView, R.id.cd_web_server_port);
            if( camera.mNetwork.WebServerPort < 0 ){
                Toast.makeText(mActivity, "Please enter a valid webserver Port", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi id
            camera.mNetwork.WiFiId = G.GetText(rootView, R.id.cd_wifi_id);
            if( camera.mNetwork.WiFiId.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid WiFi Id", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi password
            camera.mNetwork.WiFiPassword = G.GetText(rootView, R.id.cd_wifi_pwd);
            if( camera.mNetwork.WiFiPassword.isEmpty() ){
                Toast.makeText(mActivity, "Please enter a valid WiFi Password", Toast.LENGTH_SHORT).show();
                return false;
            }

            // wifi mode
            camera.mNetwork.WiFiMode = (byte)G.GetSpinnerOptions(rootView, R.id.cd_wifi_mode);
            if( camera.mNetwork.WiFiMode == -1 ){
                Toast.makeText(mActivity, "Please select a valid wifi mode from list", Toast.LENGTH_SHORT).show();
                return false;
            }

            Log.i("NetworkFragment", "Validation OK");
        } catch( Exception e ){
            e.printStackTrace();
        }
        return true;
    }

    public void SetValues() {
        try {
            // ip address
            EditText et = (EditText)rootView.findViewById(R.id.cd_ip_address);
            et.setText(camera.mNetwork.IPAddress);

            // subnet mask
            et = (EditText)rootView.findViewById(R.id.cd_subnetmask);
            et.setText(camera.mNetwork.SubnetMask);

            // gateway
            et = (EditText)rootView.findViewById(R.id.cd_gateway);
            et.setText(camera.mNetwork.Gateway);

            // com port
            et = (EditText)rootView.findViewById(R.id.cd_comm_port);
            et.setText(""+camera.mNetwork.CommPort);

            // mimg port
            et = (EditText)rootView.findViewById(R.id.cd_mimg_port);
            et.setText(""+camera.mNetwork.MImgPort);

            // webserver port
            et = (EditText)rootView.findViewById(R.id.cd_web_server_port);
            et.setText(""+camera.mNetwork.WebServerPort);

            // wifi id
            et = (EditText)rootView.findViewById(R.id.cd_wifi_id);
            et.setText(camera.mNetwork.WiFiId);

            // wifi password
            et = (EditText)rootView.findViewById(R.id.cd_wifi_pwd);
            et.setText(camera.mNetwork.WiFiPassword);

            // wifi mode
            Spinner sp = (Spinner)rootView.findViewById(R.id.cd_wifi_mode);
            sp.setSelection(camera.mNetwork.WiFiMode, true);


            Log.i("NetworkFragment", "SetValues OK");

        } catch( Exception e ){
            e.printStackTrace();
        }
    }

}
 
Anyway thanks @cricket_007 for helping me to understand the fragment tab operation

避免结构中的PhantomData强制执行类型约束(Avoiding PhantomData in a struct to enforce type constraints)

最满意答案

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