javascript - Angular 4 Firebase manipulate *ngFor of Observable or use index in an Observable -


i using angular 4 firebase database.in app want display on browser leaderboard top ten users. using code on component.ts

export class homefillercomponent implements oninit {  topusers: observable<any>;   constructor(db: angularfiredatabase,public authservice: authservice) {           this.topusers = db.list('users', {         query: {          orderbychild: "totalscore",          limittolast: 10,         }         }).map((topusers) => {console.log(topusers);         return topusers.reverse();})     }

and html code: 

<a class="btn btn-download  nav-item vlink  dropdown-toggle pointer " data-toggle="dropdown">leaderboard</a>           <ul class="dropdown-menu text-center list">                                   <ul *ngfor="let topuser of topusers | async">                                     <li> {{ topuser.username | json }}:{{ topuser.totalscore | json }} </li>                                   </ul>            </ul>         </div>

everything works fine , first 10 users.however want results shown example:

<ul>             <li><span>first:</span><span>unknow</span></li>             <li><span >second:</span><span>unknow</span></li>             <li><span >third:</span><span >unknow</span></li>             <li><span >fourth:</span><span>unknow</span></li>             <li><span >fifth</span><span>unknow</span></li>              ...etc...                     </ul>

where unknown replaced correct index of topusers observable. want control *ngfor="let topuser of topusers | async" 10 topusers can put first,second etc.. left on them. searched everywhere couldnt find on how use specific index on observable on the html code.

you can use index variable of ngfor directive

 <div *ngfor="let item of observable$ | async; let = index">      <li> {{i + 1 | ordinalstring}} {{ topuser.username | json }}:{{ topuser.totalscore | json }} </li>  </div>

then run index through pipe desired string. 

@pipe({name: 'ordinalstring'}) export class ordinalstringpipe implements pipetransform {     // super simple ordinal string method     transform(index: number): string{         let ordinalstrings = ['zero', 'first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh', 'eighth', 'ninth', 'tenth'];          return ordinalstrings[index];     } }

here working plunkr: https://plnkr.co/edit/trvaibgjb9v2ikren3uy?p=preview

here article demoing ngfor index variable: https://coryrylan.com/blog/angular-ng-for-syntax


Comments

Post a Comment

Popular posts from this blog

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m...
Read more

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

sql server - Why does Linq-to-SQL add unnecessary COUNT()? -

here tables: create table customer ( cid int primary key, name varchar(32) ) create table ord ( oid int primary key, cid int foreign key references customer, address varchar(20) ) here's linq-to-sql statement: var aaa = c in db.customer select new { c, o = c.ord.tolist() }; and here's inexplicable query generated linq-to-sql: select [t0].[cid] [cid], [t0].[name] [name], [t1].[oid] [oid], [t1].[cid] [cid2], [t1].[address] [address], (select count(*) [dbo].[ord] [t2] [t2].[cid] = [t0].[cid]) [value] [dbo].[customer] [t0] left outer join [dbo].[ord] [t1] on [t1].[cid] = [t0].[cid] order [t0].[cid], [t1].[oid] i want understand how rid of count(*) part. it's entirely uncalled for! linq needs count(*) in order determine number of entries returned o = c.ord.tolist() .
Read more