my problem is, that I have a table which should update everytime when the user chooses something from a dropdown component. The problem now is that my table updates "too late" in the frontend. So when the user chooses an option for the first time nothing will happen. Then when the user chooses an option for the second time from the dropdown component, the table will show the data from the option he has picked before. If the user chooses an option for the 3rd time, the table will show the data from the second one and so on.
So how can I fix this? I work with ReactJS and Semantic UI
My Code:
This renders the Row for the existing data
renderTableData() {
return this.state.songs.map((song, index) => {
const { id, nr, songname, link } = song
return (
<Table.Row key={id}>
<Table.Cell>{nr}</Table.Cell>
<Table.Cell>{songname}</Table.Cell>
<Table.Cell>{link}</Table.Cell>
</Table.Row>
)
})
}
The Code in the main render() function of React (Its shown correctly, expect that the data is "outdated":
`<Table>
<Table.Header>
<Table.Row>
<Table.HeaderCell width={1}>Nr</Table.HeaderCell>
<Table.HeaderCell width={2}>Songname</Table.HeaderCell>
<Table.HeaderCell width={1}>Link</Table.HeaderCell>
</Table.Row>
</Table.Header>
{this.renderTableData()}
</Table>`
The code when the option from the dropdown gets changed:
onChangeDropdown(e) {
this.setState({game: e.target.textContent}, ()=>{
this.state.songs.length = 0;
for(var i = 0; i< this.state.musicData.length;i++){
if(this.state.musicData[i].game == this.state.game){
for(var j = 0; j<this.state.musicData[i].songs.length;j++){
this.state.songs.push({id: j+1, nr: j+1, songname: this.state.musicData[i].songs[j].name, link: this.state.musicData[i].songs[j].link})
}
break;
}
}
this.renderTableData()
})
}
The game variable in this.setState is correct and also the for-loop works as expected when the user changes the dropdown option, I already checked it with the debugger
I hope you can help me out there, ty
is not that is updating too late, is that you are mutating the state without using setState so React doesn't know what changed, you should refactor your code to always use setState to update the state, not push, something like this:
onChangeDropdown(e) {
this.setState((currentState) => {
const newSongs = [];
const game = e.target.textContent;
musicData.forEach((data) => {
if (data.game === game) {
musicData.songs.forEach((song, index) => {
newSongs.push({
id: index + 1,
nr: index + 1,
songname: song.name,
link: song.link,
});
});
}
});
return {
...currentState,
game,
songs: newSongs,
};
});
}
I changed your for loops to use forEach, less complexity, easier to read
Here is what I did:
create a empty array to store the selected songs (newSongs)
loop all the music data and then loop all the songs inside each item in music data
add the songs from the selected game into newSongs
return newSongs + game to update the selected game, ...currentState is to preserve the other parts of the state between changes
So every time the dropodown changes, I create a new array and run the logic
The setState callback can return an object to replace whole state, so before that you can do any calculation you need to.
Updating the state in React is asyncronous, that's one of the reasons you can't mutate the state directly and need to use setState any time you need to update it
Related
New to react... Really banging my head against it with this one... I'm trying to figure out how to get a dynamically inserted component to update when the props are changed. I've assigned it to a parent state object but it doesn't seem to re-render. I've read that this is what's supposed to happen.
I was using ReactDOM.unmountComponentAtNode to re-render the specific elements I needed to, but it kept yelling at me with red text.
I need to hide "chat.message" unless the user has the authority to see it (server just sends empty string), but I still need to render the fact that it exists, and reveal it should the user get authentication. I'm using a css transition to reveal it, but I really need a good way to update the chat.message prop easily.
renderChats(uuid){
let userState = this.state.userStates.find(user => {
return user.uuid === uuid;
});
const children = userState.chats.map((chat) => {
let ChatReactElement = this.getChatMarkup(chat.cuid, chat.message, chat.status);
return ChatReactElement;
});
ReactDOM.render(children, document.getElementById(`chats-${this.state.guid}-${uuid}`));
}
getChatMarkup() just returns JSX and inserts Props... I feel like state should be getting passed along here. Even when I use a for-loop and insert the state explicitly, it doesn't seem to re-render on changes.
getChatMarkup(cuid, message, status){
return(
<BasicChatComponent
key={cuid}
cuid={cuid}
message={message}
status={status}
/>
);
}
I attempted to insert some code line this:
renderChats(uuid){
let userState = this.state.userStates.find(user => {
return user.uuid === uuid;
});
const children = userState.chats.map((chat) => {
let ChatReactElement = this.getChatMarkup(chat.cuid, chat.message, chat.status);
if(chat.status.hidden)
this.setState({ hiddenChatRE: [ ...this.state.hiddenChatRE, ChatReactElement ] }); // <== save elements
return ChatReactElement;
});
ReactDOM.render(children, document.getElementById(`chats-${this.state.guid}-${uuid}`));
}
and later in my code:
this.state.hiddenChatRE.every(ReactElement => {
if(ReactElement.key == basicChats[chatIndex].cuid){
ReactElement.props = {
... //completely invalid code
}
}
});
The only response I see here is my ReactDOM.unmountComponentAtNode(); approach...
Can anyone point me in the right direction here?
Although perhaps I should be kicking myself, I read up on how React deals with keys on their components. So there's actually a fairly trivial answer here if anyone comes looking... Just call your render function again after you update the state.
In my case, something like:
this.setState(state =>({
...state,
userStates : state.userStates.map((userstate) => {
if(userstate.uuid == basicChats[chatIndex].uuid) return {
...userstate,
chats: userstate.chats.map((chat) => {
if(chat.cuid == basicChats[chatIndex].cuid){
//
return {
cuid: basicChats[chatIndex].cuid,
message: basicChats[chatIndex].message,
status: basicChats[chatIndex].status
}
}
else return chat;
})
}
else return userstate;
})
}));
and then, elsewhere in my example:
this.state.userStates.map((userstate) => {
this.renderChats(userstate.uuid);
});
Other than the fact that I'd recommend using indexed arrays for this example to cut complexity, this is the solution, and works. This is because even though it feels like you'd end up with duplicates (that was my intuition), the uid on the BasicChatComponent itself makes all the difference, letting react know to only re-render those specific elements.
Relative newbie; forgive me if my etiquette and form here aren't great. I'm open to feedback.
I have used create-react-native-app to create an application using PouchDB (which I believe ultimately uses AsyncStorage) to store a list of "items" (basically).
Within a TabNavigator (main app) I have a StackNavigator ("List screen") for the relevant portion of the app. It looks to the DB and queries for the items and then I .map() over each returned record to generate custom ListView-like components dynamically. If there are no records, it alternately displays a prompt telling the user so. In either case, there is an "Add Item" TouchableOpacity that takes them to a screen where they an add a new item (for which they are taken to an "Add" screen).
When navigating back from the "Add" screen I'm using a pattern discussed quite a bit here on SO in which I've passed a "refresh" function as a navigation param. Once the user uses a button on the "Add" screen to "save" the changes, it then does a db.post() and adds them item, runs the "refresh" function on the "List screen" and then navigates back like so:
<TouchableOpacity
style={styles.myButton}
onPress={() => {
if (this.state.itemBrand == '') {
Alert.alert(
'Missing Information',
'Please be sure to select a Brand',
[
{text: 'OK', onPress: () =>
console.log('OK pressed on AddItemScreen')},
],
{ cancelable: false }
)
} else {
this.createItem();
this.props.navigation.state.params.onGoBack();
this.props.navigation.navigate('ItemsScreen');
}
}
}
>
And all of this works fine. The "refresh" function (passed as onGoBack param) works fine... for this screen. The database is called with the query, the new entry is found and the components for the item renders up like a charm.
Each of the rendered ListItem-like components on the "List screen" contains a react-native-slideout with an "Edit" option. An onPress for these will send the user to an "Item Details" screen, and the selected item's _id from PouchDB is passed as a prop to the "Item Details" screen where loadItem() runs in componentDidMount and does a db.get(id) in the database module. Additional details are shown from a list of "events" property for that _id (which are objects, in an array) which render out into another bunch of ListItem-like components.
The problem arises when either choose to "Add" an event to the list for the item... or Delete it (using another function via [another] slideout for these items. There is a similar backward navigation, called in the same form as above after either of the two functions is called from the "Add Event" screen, this being the "Add" example:
async createEvent() {
var eventData = {
eventName: this.state.eventName.trim(),
eventSponsor: this.state.eventSponsor.trim(),
eventDate: this.state.eventDate,
eventJudge: this.state.eventJudge.trim(),
eventStandings: this.state.eventStandings.trim(),
eventPointsEarned: parseInt(this.state.eventPointsEarned.trim()),
};
var key = this.key;
var rev = this.rev;
await db.createEvent(key, rev, eventData);
}
which calls my "db_ops" module function:
exports.createEvent = function (id, rev, eventData) {
console.log('You called db.createEvent()');
db.get(id)
.then(function(doc) {
var arrWork = doc.events; //assign array of events to working variable
console.log('arrWork is first assigned: ' + arrWork);
arrWork.push(eventData);
console.log('then, arrWork was pushed and became: ' + arrWork);
var arrEvents = arrWork.sort((a,b)=>{
var dateA = new Date(a.eventDate), dateB = new Date(b.eventDate);
return b.eventDate - a.eventDate;
})
doc.events = arrEvents;
return db.put(doc);
})
.then((response) => {
console.log("db.createEvent() response was:\n" +
JSON.stringify(response));
})
.catch(function(err){
console.log("Error in db.createEvent():\n" + err);
});
}
After which the "Add Event" screen's button fires the above in similar sequence to the first, just before navigating back:
this.createEvent();
this.props.navigation.state.params.onGoBack();
this.props.navigation.navigate('ItemsDetails');
The "refresh" function looks like so (also called in componentDidMount):
loadItem() {
console.log('Someone called loadItem() with this.itemID of ' + this.itemID);
var id = this.itemID;
let totalWon = 0;
db.loadItem(id)
.then((item) => {
console.log('[LOAD ITEM] got back data of:\n' + JSON.stringify(item));
this.setState({objItem: item, events: item.events});
if (this.state.events.length != 0) { this.setState({itemLoaded: true});
this.state.events.map(function(event) {
totalWon += parseInt(event.eventPointsEarned);
console.log('totalWon is ' + totalWon + ' with ' +
event.eventPointsEarned + ' having been added.');
});
};
this.setState({totalWon: totalWon});
})
.catch((err) => {
console.log('db.loadItem() error: ' + err);
this.setState({itemLoaded: false});
});
}
I'm at a loss for why the List Screen refreshes when I add an item... but not when I'm doing other async db operations with PouchDB in what I think is similar fashion to modify the object containing the "event" information and then heading back to the Item Details screen.
Am I screwing up with Promise chain someplace? Neglecting behavior of the StackNavigator when navigating deeper?
The only other difference being that I'm manipulating the array in the db function in the non-working case, whereas the others I'm merely creating/posting or deleting/removing the record, etc. before going back to update state on the prior screen.
Edit to add, as per comments, going back to "List screen" and the opening "Item Details" does pull the database data and correctly shows that the update was made.
Further checking I've done also revealed that the console.log in createEvent() to print the response to the db call isn't logging until after some of the other dynamic rendering methods are getting called on the "Item Details" screen. So it seems as though the prior screen is doing the get() that loadItem() calls before the Promise chain in createEvent() is resolving. Whether the larger issue is due to state management is still unclear -- though it would make sense in some respects -- to me as this could be happening regardless of whether I've called my onGoBack() function.
Edit/bump: I’ve tried to put async/await to use in various places in both the db_ops module on the db.get() and the component-side loadItem() which calls it. There’s something in the timing of these that just doesn’t jive and I am just totally stuck here. Aside from trying out redux (which I think is overkill in this particular case), any ideas?
There is nothing to do with PDB or navigation, it's about how you manage outer changes in your depending (already mounted in Navigator since they are in history - it's important to understand - so componentDidMount isn't enough) components. If you don't use global state redux-alike management (as I do) the only way to let know depending component that it should update is passing corresponding props and checking if they were changed.
Like so:
//root.js
refreshEvents = ()=> { //pass it to DeleteView via screenProps
this.setState({time2refreshEvents: +new Date()}) //pass time2refreshEvents to EventList via screenProps
}
//DeleteView.js
//delete button...
onPress={db.deleteThing(thingID).then(()=> this.props.screenProps.refreshEvents())}
//EventList.js
...
constructor(props) {
super(props);
this.state = {
events: [],
noEvents: false,
ready: false,
time2refreshEvents: this.props.screenProps.time2refreshEvents,
}
}
static getDerivedStateFromProps(nextProps, currentState) {
if (nextProps.screenProps.time2refreshEvents !== currentState.time2refreshEvents ) {
return {time2refreshEvents : nextProps.screenProps.time2refreshEvents }
} else {
return null
}
}
componentDidMount() {
this._getEvents()
}
componentDidUpdate(prevProps, prevState) {
if (this.state.time2refreshEvents !== prevState.time2refreshEvents) {
this._getEvents()
}
}
_getEvents = ()=> {
//do stuff querying db and updating your list with actual data
}
I have a Component, which have child component. at ngOnInit() I'm calling Web API and get list of data.
Initial point length of the list is 10, But it will have more.
Need to execute some method (task|process|job) in background to take rest of the data 10 by 10 in a loop which would run parallel to other task in background no matter what the user is currently doing, which component he/she is interacting with. And execute that method so that it doesn't block others.
What is the correct way to do this?
Seems like a recursive call to me !
firstResults: any[] = []; // First 10 results to show to your user
results: any[] = []; // All results
currentPosition = 0; // The current position of your last result fetched
getData() {
this.myService.getResults().subscribe(results => {
if(!this.firstResults.length) {
this.firstResults = results
}
this.results.push(...results);
this.currentPosition += results.length;
this.getData();
});
}
I don't imagine you're trying to do. But if the list is not so largger, you can get all the data and "paginate" the array
allData:any[];
page:number=0; //page is 0,1,2,3,4....
paginateData:any[]
this.httpClient.get("url").subscribe(res=>{
allData=res;
paginateData=allData.slice(10*this.page,10*(this.page+1));
}
I am building an Electron based application that contains a grid containing unique rows. I would like a context-menu that is specific to each row. Here is an example:
Although this screen shot is cropped, you can see there are multiple rows and each row contains separate data. Since I'd like to right-click on a row and get a unique context menu, I have implemented electron-context-menu, which does work on the first right click, but then subsequent right-clicks causes a stacking effect of context menus.
Specifically, here is what happens:
I right click on Row-1 and the proper context menu shows up
I right click on Row-2 and a repeat of the context menu for Row-1 shows up then Row-2's context menu shows up. (Notice in the screen shot the context menu showing does not correspond to the row my mouse is over)
This repeats itself.
In React.JS, here is my listener, which collects the contextmenu object as needed by the electron-context-menu module:
handleContextMenu() {
this.props.contextMenu({
window: electron.remote.BrowserWindow.getFocusedWindow(),
prepend: (params, browserWindow) => [{
label: `Library Compare ${this.state.msn}`,
click: () => this.runLibCompare()
}],
append: (params, browserWindow) => [{
label: '---',
}]
})
};
Where this.props.contextMenu(...) perculates up the React.JS components to be fed into:
const contextMenu = eRequire('electron-context-menu');
I have done some massive debugging and I don't think the issue is the module. The module I am using essentially organizes the information about the context menu and then uses electron.remote functions and a menu.popup function which comes from electron internals. Here is a link to the specific line in github.
const menu = (electron.Menu || electron.remote.Menu).buildFromTemplate(menuTpl);
menu.popup(electron.remote ? electron.remote.getCurrentWindow() : win);
This call to menu.popup leads to this line in electron.
const remoteMemberFunction = function (...args) {
if (this && this.constructor === remoteMemberFunction) {
// Constructor call.
let ret = ipcRenderer.sendSync('ELECTRON_BROWSER_MEMBER_CONSTRUCTOR', metaId, member.name, wrapArgs(args))
return metaToValue(ret)
} else {
// Call member function.
let ret = ipcRenderer.sendSync('ELECTRON_BROWSER_MEMBER_CALL', metaId, member.name, wrapArgs(args))
return metaToValue(ret)
}
}
So I see a call to ipcRender.sendSync -- however when I add debugging statements in ipcMain's receiver of those calls, I don't see any output!
ipcMain.on('ELECTRON_BROWSER_MEMBER_CALL', function (event, id, method, args) {
try {
args = unwrapArgs(event.sender, args)
let obj = objectsRegistry.get(id)
if (obj == null) {
throwRPCError(`Cannot call function '${method}' on missing remote object ${id}`)
}
callFunction(event, obj[method], obj, args)
} catch (error) {
event.returnValue = exceptionToMeta(error)
}
})
When I added debug statements to the above function, I didn't see any output. And that is where my search his a wall.
I am using electron 1.4.15. I know this issue should be resolvable, after-all the Atom IDE (which is electron based) does not have this issue even though it has multiple context menus.
I think there is some memory I need to clear somewhere, I just can't figure out how to clear the stack of previous context menus!
I solve this by first getting the target of the click using e.target. Then, depending on that, I call the corresponding contextmenu. If target hit is not in the list of targets for my app, I use a default contextmenu.
window.addEventListener(
"contextmenu",
e => {
e.preventDefault();
if (e.target.id === 'fullscr'){
console.log(e && e.target);
// e.preventDefault();
mymenu.popup(remote.getCurrentWindow());
}else{
editmenu.popup(remote.getCurrentWindow());
}
console.log(e.which);
},
false
);
There are two collections products and stock in my database.Each product have multipple stock with different supplier and attributes of products.
I have selected the products from products collection and run a loop for each product. I need to append price and offer price from the stock collection to products i have selected already.
I think the for loop compleated its execution before executiong the find method on stock collection.I need to execute everything in the loop in serial manner(not asynchronous). Please check the code below and help me to solve this. I'm new in node.js and mongodb
collection = db.collection('products');
collection.find().toArray(function(err, abc) {
var finalout = [];
for( var listProducts in abc){
var subfinal = {
'_id' :abc[listProducts]['_id'],
'min_price' :abc[listProducts]['value']['price'],
'stock' :abc[listProducts]['value']['stock'],
'name' :abc[listProducts]['value']['name'],
'price' :'',
'offer_price' :'',
};
collection = db.collection('stock');
collection.find({"product":abc[listProducts]['_id'] ,"supplier":abc[listProducts]['value']['def_supplier']}).toArray(function(err, newprod) {
for( var row in newprod){
subfinal['price'] = newprod[row]['price'];
subfinal.offer_price = newprod[row]['offer_price'];
}
finalout.push(subfinal);
});
}
console.log(finalout);
});
Yes, the loop is running and starting the get requests on the database all at the same time. It is possible, like you said, to run them all sequentially, however it's probably not what you're looking for. Doing it this way will take more time, since each request to Mongo would need to wait for the previous one to finish.
Considering that each iteration of the loop doesn't depend on the previous ones, all you're really looking for is a way to know once ALL of the operations are finished. Keep in mind that these can end in any order, not necessarily the order in which they were initiated in the loop.
There's was also an issue in the creation of the subfinal variable. Since the same variable name is being used for all iterations, when they all come back they'll be using the final assignment of the variable (all results will be written on the same subfinal, which will have been pushed multiple times into the result). To fix that, I've wrapped the entire item processing iteration into another function to give each subfinal variable it's own scope.
There are plenty of modules to ease this kind of management, however here is one way to run some code only after all the Mongo calls are finished using a counter and callback that doesn't require any additional installs:
var finished = 0; // incremented every time an iteration is done
var total = Object.keys(abc).length; // number of keys in the hash table
collection = db.collection('products');
collection.find().toArray(function(err, abc) {
var finalout = [];
for( var listProducts in abc){
processItem(listProducts);
}
});
function processItem(listProducts) {
var subfinal = {
'_id' :abc[listProducts]['_id'],
'min_price' :abc[listProducts]['value']['price'],
'stock' :abc[listProducts]['value']['stock'],
'name' :abc[listProducts]['value']['name'],
'price' :'',
'offer_price' :'',
};
collection = db.collection('stock');
collection.find({"product":abc[listProducts]['_id'] ,"supplier":abc[listProducts]['value']['def_supplier']}).toArray(function(err, newprod) {
for( var row in newprod){
subfinal['price'] = newprod[row]['price'];
subfinal.offer_price = newprod[row]['offer_price'];
}
finalout.push(subfinal);
finished++;
if (finished === total) { // if this is the last one to finish.
allFinished(finalout);
}
});
}
function allFinished(finalout) {
console.log(finalout);
}
It could be written more concisely with less variables, but it should be easier to understand this way.