bagaimana memperbaiki batas render loop dalam bereaksi

Nov 28 2020

Saya sedang membangun aplikasi chat menggunakan react dan Firebase real time database.

saya punya masalah dengan rendering batas maksimum karena hook usecallback dan status pengguna (hook adalah addOnConnectLister addOnDisConnectListner).

ini kodenya:

import React, { useEffect, useState, useCallback, useRef } from "react";
import { Icon, Menu } from "semantic-ui-react";
import firebase from "../../firebase";

const DirectMessages = (props) => {
  const [usersRef] = useState(firebase.database().ref("users"));
  const [connectedRef] = useState(firebase.database().ref(".info/connected"));
  const [presenceRef] = useState(firebase.database().ref("presence"));
  const [users, setUsers] = useState([]);

  //add presence listner
  //create a presence record for current user
  const addPressenceListner = useCallback(
    (currentUserID) => {
      connectedRef.on("value", (snap) => {
        console.log("connecting snap value", snap.val());
        if (snap.val()) {
          const ref = presenceRef.child(currentUserID);
          ref.set(true);
       ref.onDisconnect().remove((err) => {
            if (err) console.log(err);
          });
        }
      });
    },
    [connectedRef, presenceRef]
  );


  //init connected users
  const initUsers = useCallback(
    (currentUserID) => {
      const loadedUsers = [];
      usersRef.on("child_added", (snap) => {
        if (currentUserID !== snap.key) {
          let user = snap.val();
          user["uid"] = snap.key;
          user["status"] = "offline";
          loadedUsers.push(user);
          setUsers([...loadedUsers]);
        }
      });
    },
    [usersRef]
  );

  //update user status when go online
  const addOnConnectListner = useCallback(() => {
    presenceRef.on("child_added", (snap) => {
      const updatedUsers = users.map((user) => {
        if (user.uid === snap.key) {
          console.log("user connected", user);
          user["status"] = "online";
        }
        return user;
      });
      setUsers(...[updatedUsers]);
    });
  }, [presenceRef, users]);

  //update user status when go offline
  const addOnDisconnectListner = useCallback(() => {
    presenceRef.on("child_removed", (snap) => {
      const updatedUsers = users.map((user) => {
        if (user.uid === snap.key) {
          console.log("user disconnected", user);
          user["status"] = "offline";
        }
        return user;
      });
      setUsers(updatedUsers);
    });
  }, [users, presenceRef]);

  const addListners = useCallback(
    (currentUserID) => {
      addPressenceListner(currentUserID);
      initUsers(currentUserID);
      addOnConnectListner();
      addOnDisconnectListner();
    },
    [
      addOnConnectListner,
      addOnDisconnectListner,
      addPressenceListner,
      initUsers,
    ]
  );

  useEffect(() => {
    if (props.currentUser) {
      addListners(props.currentUser.uid);
    }
    return () => {
      presenceRef.off();
      usersRef.off();
      connectedRef.off();
    };
  }, [props.currentUser, addListners, connectedRef, presenceRef, usersRef]);

  const isUserOnline = (user) => user.status === "online";

  return (
    <Menu.Menu className="menu" style={{ paddingTop: "2em" }}>
      <Menu.Item>
        <span>
          <Icon name="mail" /> Direct Messages
        </span>{" "}
        ({users.length})
      </Menu.Item>

      {users.map((user) => (
        <Menu.Item key={user.uid}>
          <Icon name="circle" color={isUserOnline(user) ? "green" : "red"} />@
          {user.username}
        </Menu.Item>
      ))}
    </Menu.Menu>
  );
};

export default DirectMessages;

setelah mencari saya menemukan solusi menggunakan useRef untuk mendapatkan referensi status pengguna untuk menghindari masalah tetapi tidak berfungsi dengan benar callback hanya dijalankan sekali

import React, { useEffect, useState, useCallback, useRef } from "react";
import { Icon, Menu } from "semantic-ui-react";
import firebase from "../../firebase";

const DirectMessages = (props) => {
  const [usersRef] = useState(firebase.database().ref("users"));
  const [connectedRef] = useState(firebase.database().ref(".info/connected"));
  const [presenceRef] = useState(firebase.database().ref("presence"));
  const [users, setUsers] = useState([]);

  //users state ref
  const getUsersRef = useRef(users);

  useEffect(() => {
    getUsersRef.current = users;
  }, [users]);

  //add presence listner
  //create a presence record for current user
  const addPressenceListner = useCallback(
    (currentUserID) => {
      connectedRef.on("value", (snap) => {
        console.log("connecting snap value", snap.val());
        if (snap.val()) {
          const ref = presenceRef.child(currentUserID);
          ref.set(true);
          ref.onDisconnect().remove((err) => {
            if (err) console.log(err);
          });
        }
      });
    },
    [connectedRef, presenceRef]
  );


  //init connected users
  const initUsers = useCallback(
    (currentUserID) => {
      const loadedUsers = [];
      usersRef.on("child_added", (snap) => {
        if (currentUserID !== snap.key) {
          let user = snap.val();
          user["uid"] = snap.key;
          user["status"] = "offline";
          loadedUsers.push(user);
          setUsers([...loadedUsers]);
        }
      });
    },
    [usersRef]
  );

  //update user status when go online
  const addOnConnectListner = useCallback(() => {
    presenceRef.on("child_added", (snap) => {
      const updatedUsers = getUsersRef.current.map((user) => {
        if (user.uid === snap.key) {
          console.log("user connected", user);
          user["status"] = "online";
        }
        return user;
      });
      setUsers(...[updatedUsers]);
    });
  }, [presenceRef, getUsersRef]);

  //update user status when go offline
  const addOnDisconnectListner = useCallback(() => {
    presenceRef.on("child_removed", (snap) => {
      const updatedUsers = getUsersRef.current.map((user) => {
        if (user.uid === snap.key) {
          console.log("user disconnected", user);
          user["status"] = "offline";
        }
        return user;
      });
      setUsers(updatedUsers);
    });
  }, [getUsersRef, presenceRef]);

  const addListners = useCallback(
    (currentUserID) => {
      addPressenceListner(currentUserID);
      initUsers(currentUserID);
      addOnConnectListner();
      addOnDisconnectListner();
    },
    [
      addOnConnectListner,
      addOnDisconnectListner,
      addPressenceListner,
      initUsers,
    ]
  );

  useEffect(() => {
    if (props.currentUser) {
      addListners(props.currentUser.uid);
    }
    return () => {
      presenceRef.off();
      usersRef.off();
      connectedRef.off();
    };
  }, [props.currentUser, addListners, connectedRef, presenceRef, usersRef]);

  const isUserOnline = (user) => user.status === "online";

  return (
    <Menu.Menu className="menu" style={{ paddingTop: "2em" }}>
      <Menu.Item>
        <span>
          <Icon name="mail" /> Direct Messages
        </span>{" "}
        ({users.length})
      </Menu.Item>

      {users.map((user) => (
        <Menu.Item key={user.uid}>
          <Icon name="circle" color={isUserOnline(user) ? "green" : "red"} />@
          {user.username}
        </Menu.Item>
      ))}
    </Menu.Menu>
  );
};

export default DirectMessages;

Jawaban

SomeoneSpecial Nov 29 2020 at 13:08

pertama, Anda tidak membutuhkannya sebagai negara

  const [usersRef] = useState(firebase.database().ref("users"));
  const [connectedRef] = useState(firebase.database().ref(".info/connected"));
  const [presenceRef] = useState(firebase.database().ref("presence"));

mengaturnya di luar komponen.

const usersRef = firebase.database().ref("users")
const connectedRef = firebase.database().ref(".info/connected")
const presenceRef = firebase.database().ref("presence")

const DirectMessages = (props) => {
......

Kedua, cara yang benar untuk menghilangkan pendengar adalah.

 useEffect(() => {
    if (props.currentUser) {
      addListners(props.currentUser.uid);
    return () => {
      presenceRef.off('child_added');
      presenceRef.off('child_removed');
      usersRef.off('child_added');
      connectedRef.off('value');
    };
    }

  }, [props.currentUser, addListners, connectedRef, presenceRef, usersRef]);

Saya akan mengubah yang berikut ini

  const [users, setUsers] = useState([]);

  //users state ref
  const getUsersRef = useRef(users);

  useEffect(() => {
    getUsersRef.current = users;
  }, [users]);

untuk

  const [users, _setUsers] = useState([]);
  const getUsersRef = useRef(users);

  const setUsers = (array) => {
        getUsersRef.current = array;
        _setUsers(array)
  }

terakhir , usecallback tidak diperlukan, Anda harus membuatnya sebagai fungsi biasa.

  const addOnDisconnectListner = () => {
    presenceRef.on("child_removed", (snap) => {
      const updatedUsers = getUsersRef.current.map((user) => {
        if (user.uid === snap.key) {
          console.log("user disconnected", user);
          user["status"] = "offline";
        }
        return user;
      });
      setUsers(updatedUsers);
    }
B.Fateh Nov 29 2020 at 14:51

mengubah ini:

  const [users, setUsers] = useState([]);

  //users state ref
  const getUsersRef = useRef(users);

  useEffect(() => {
    getUsersRef.current = users;
  }, [users]);

untuk ini:

  //users state ref
  const getUsersRef = useRef(users);

  useEffect(() => {
    getUsersRef.current = users;
  }, [users]);

setelah memperbarui dependensi hook:

import React, { useEffect, useState, useCallback, useRef } from "react";
import { Icon, Menu } from "semantic-ui-react";
import firebase from "../../firebase";

const usersRef = firebase.database().ref("users");
const connectedRef = firebase.database().ref(".info/connected");
const presenceRef = firebase.database().ref("presence");

const DirectMessages = (props) => {
  const [users, _setUsers] = useState([]);

  //get users ref
  const getUsersRef = useRef(users);

  const setUsers = (array) => {
    getUsersRef.current = array;
    _setUsers(array);
  };

  //add presence listner
  //create a presence record for current user
  const addPressenceListner = useCallback((currentUserID) => {
    connectedRef.on("value",(snap) => {
      console.log("connecting snap value", snap.val());
      if (snap.val()) {
        const ref = presenceRef.child(currentUserID);
        ref.set(true);
        ref.onDisconnect().remove((err) => {
          if (err) console.log(err);
        });
      }
    });
  }, []);

  //init connected users
  const initUsers = useCallback((currentUserID) => {
    const loadedUsers = [];
    usersRef.on("child_added", (snap) => {
      if (currentUserID !== snap.key) {
        let user = snap.val();
        user["uid"] = snap.key;
        user["status"] = "offline";
        loadedUsers.push(user);
        setUsers([...loadedUsers]);
      }
    });
  }, []);

  //update user status when go online
  const addOnConnectListner = useCallback(() => {
    presenceRef.on("child_added", (snap) => {
      const updatedUsers = getUsersRef.current.map((user) => {
        if (user.uid === snap.key) {
          user["status"] = "online";
        }
        console.log("user", user);
        return user;
      });
      setUsers(...[updatedUsers]);
    });
  }, []);

  //update user status when go offline
  const addOnDisconnectListner = useCallback(() => {
    presenceRef.on("child_removed", (snap) => {
      const updatedUsers = getUsersRef.current.map((user) => {
        if (user.uid === snap.key) {
          console.log("user disconnected", user);
          user["status"] = "offline";
        }
        return user;
      });
      setUsers(updatedUsers);
    });
  }, [getUsersRef]);

  const addListners = useCallback(
    (currentUserID) => {
      addPressenceListner(currentUserID);
      initUsers(currentUserID);
      addOnConnectListner();
      addOnDisconnectListner();
    },
    [
      addOnConnectListner,
      addOnDisconnectListner,
      addPressenceListner,
      initUsers,
    ]
  );

  useEffect(() => {
    if (props.currentUser) {
      addListners(props.currentUser.uid);
    }
    return () => {
      presenceRef.off();
      usersRef.off();
      connectedRef.off();
    };
  }, [props.currentUser, addListners]);

  const isUserOnline = (user) => user.status === "online";

  return (
    <Menu.Menu className="menu" style={{ paddingTop: "2em" }}>
      <Menu.Item>
        <span>
          <Icon name="mail" /> Direct Messages
        </span>{" "}
        ({users.length})
      </Menu.Item>

      {users.map((user) => (
        <Menu.Item key={user.uid}>
          <Icon name="circle" color={isUserOnline(user) ? "green" : "red"} />@
          {user.username}
        </Menu.Item>
      ))}
    </Menu.Menu>
  );
};

export default DirectMessages;