Angular Material - How to refresh a data source mat-table

Question

I am using a mat-table to list the content of the users chosen languages  They can also add new languages using dialog panel  After they added a language and returned back  I want my datasource to refresh to show the changes they made    I initialize the datastore by getting user data from a service and passing that into a datasource in the refresh method     Language component ts  import   Component  OnInit   from   angular core   import   LanguageModel  LANGUAGE DATA   from              models language model   import   LanguageAddComponent   from    language-add language-add component   import   AuthService   from              services auth service   import   LanguageDataSource   from    language-data-source   import   LevelbarComponent   from              directives levelbar levelbar component   import   DataSource   from   angular cdk collections   import   Observable   from  rxjs Observable   import  rxjs add observable of   import   MatSnackBar  MatDialog   from   angular material     Component     selector   app-language     templateUrl     language component html     styleUrls      language component scss      export class LanguageComponent implements OnInit      displayedColumns     name    native    code    level      teachDS  any    user  any     constructor private authService  AuthService  private dialog  MatDialog         ngOnInit         this refresh           add         this dialog open LanguageAddComponent          data    user  this user           afterClosed   subscribe result   gt          this refresh                   refresh         this authService getAuthenticatedUser   subscribe  res    gt          this user   res        this teachDS   new LanguageDataSource this user profile languages teach                      language-data-source ts  import  MatPaginator  MatSort  from   angular material   import  DataSource  from   angular cdk collections   import  Observable  from  rxjs Observable   import  rxjs add observable merge   import  rxjs add operator map    export class LanguageDataSource extends DataSource lt any gt       constructor private languages        super           connect    Observable lt any gt        return Observable of this languages          disconnect            No-op          So I have tried to call a refresh method where I get the user from the backend again and then I reinitialize the data source  However this does not work  no changes are occurring

User · Answer

I had tried ChangeDetectorRef  Subject and BehaviourSubject but what works for me  dataSource       this dataSource        setTimeout      gt        this dataSource   this tableData data      200

User · Answer

I don t know if the ChangeDetectorRef was required when the question was created  but now this is enough   import   MatTableDataSource   from   angular material table            dataSource   new MatTableDataSource lt MyDataType gt      refresh       this myService doSomething   subscribe  data  MyDataType      gt        this dataSource data   data          Example  StackBlitz

User · Answer

This worked for me   refreshTableSorce         this dataSource   new MatTableDataSource lt Element gt  this newSource

User · Answer

in my case  Angular 6    I inherited from MatTableDataSource to create MyDataSource  Without calling after this data   someArray  this entitiesSubject next this data as T      data where not displayed  class MyDataSource  export class MyDataSource lt T extends WhateverYouWant gt  extends MatTableDataSource lt T gt         private entitiesSubject   new BehaviorSubject lt T   gt             loadDataSourceData someArray  T             this data   someArray   whenever it comes from an API asyncronously or not         this entitiesSubject next this data as T      Otherwise data not displayed            public connect    BehaviorSubject lt T   gt            return this entitiesSubject           end Class

User · Answer

After reading Material Table not updating post data update  11638 Bug Report I found the best  read  the easiest solution  was as suggested by the final commentor  shhdharmen  with a suggestion to use an EventEmitter   This involves a few simple changes to the generated datasource class  ie  add a new private variable to your datasource class  import   EventEmitter   from   angular core       private tableDataUpdated   new EventEmitter lt any gt       and where I push new data to the internal array  this data   I emit an event   public addRow row myRowInterface        this data push row       this tableDataUpdated emit        and finally  change the  dataMutation  array in the  connect  method - as follows  const dataMutations         this tableDataUpdated      this paginator page      this sort sortChange

User · Answer

this is the dataSource this guests        this guests push  id  1  name   Ricardo         refresh the dataSource this guests   Array from this guest

User · Answer

I think the MatTableDataSource object is some way linked with the data array that you pass to MatTableDataSource constructor   For instance   dataTable  string    tableDS  MatTableDataSource lt string gt    ngOnInit          here your pass dataTable to the dataSource    this tableDS   new MatTableDataSource this dataTable        So  when you have to change data  change on the original list dataTable and then reflect the change on the table by call  updateChangeSubscription   method on tableDS   For instance   this dataTable push  testing    this tableDS  updateChangeSubscription      That s work with me through Angular 6

User · Answer

this dataSource   new MatTableDataSource lt Element gt  this elements     Add this line below your action of add or delete the particular row   refresh       this authService getAuthenticatedUser   subscribe  res    gt        this user   new MatTableDataSource lt Element gt  res

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import   Subject   from  rxjs Subject   import   Observable   from  rxjs Observable    export class LanguageComponent implemnts OnInit     displayedColumns     name    native    code    leavel      user  any    private update   new Subject lt void gt       update    this update asObservable       constructor private authService  AuthService  private dialog  MatDialog         ngOnInit          this update  subscribe      gt    this refresh               setUpdate          this update next             add          this dialog open LanguageAddComponent         data    user  this user          afterClosed   subscribe result   gt         this setUpdate                refresh        this authService getAuthenticatedUser   subscribe  res    gt         this user   res       this teachDS   new LanguageDataSource this user profile languages teach

User · Answer

Well  I ran into a similar problem where I added somthing to the data source and it s not reloading   The easiest way I found whas simply to reassigning the data  let dataSource     a   b   c   dataSource push  d   let cloned   dataSource slice      OR IN ES6    let cloned       dataSource  dataSource   cloned

User · Answer

I have tried some of the previous suggestions  It does update the table but I have some concerns   Updating dataSource data with its clone  e g   this dataSource data       this dataSource data    If the data is large  this will reallocate lot of memory  Moreover  MatTable thinks that everything is new inside the table  so it may cause performance issue  I found my table flickers where my table has about 300 rows   Calling paginator  changePageSize  e g   this paginator  changePageSize this paginator pageSize    It will emit page event  If you have already had some handling for the page event  You may find it weird because the event may be fired more than once  And there can be a risk that if somehow the event will trigger  changePageSize   indirectly  it will cause infinite loop    I suggest another solution here  If your table is not relying on dataSource s filter field   You may update the filter field to trigger table refresh   this dataSource filter           Note that it is a space  not empty string  By doing so  the table will perform filtering and thus updating the UI of the table  But it requires having your own dataSource filterPredicate   to handling your filtering logic

User · Answer

Best way to do this is by adding an additional observable to your Datasource implementation   In the connect method you should already be using Observable merge to subscribe to an array of observables that include the paginator page  sort sortChange  etc   You can add a new subject to this and call next on it when you need to cause a refresh   something like this   export class LanguageDataSource extends DataSource lt any gt         recordChange    new Subject         constructor private languages          super               connect    Observable lt any gt           const changes             this recordChange                  return Observable merge    changes           switchMap      gt  return Observable of this languages               disconnect              No-op           And then you can call recordChange  next   to initiate a refresh   Naturally I would wrap the call in a refresh   method and call it off of the datasource instance w in the component  and other proper techniques

User · Answer

You can also use renderRows   method    ViewChild MatTable   static  false   table   MatTable     initialize  then    this table renderRows     for reference check this out -  https   www freakyjolly com angular-7-8-edit-add-delete-rows-in-material-table-with-using-dialogs-inline-row-operation

User · Answer

This is working for me   dataSource   new MatTableDataSource lt Dict gt           public search             let url      Constants API COMMON  dicts page   this page number  amp               this name               name like   this name         this  http get lt Dict gt  url  subscribe  data   gt           this dataSource   data   embedded   dicts      this dataSource data    data   embedded   dicts      this page   data  page        this resetSelection              So you should declare your datasource instance as MatTableDataSource

User · Answer

You can easily update the data of the table using  concat    for example   language component ts  teachDS  any           language component html   lt table mat-table  dataSource   teachDS  class  list  gt    And  when you update the data  language component ts    addItem            newItem is the object added to the list using a form or other way     this teachDS   this teachDS concat  newItem         When you re using  concat  angular detect the changes of the object  this teachDS  and you don t need to use another thing   PD  It s work for me in angular 6 and 7  I didn t try another version

User · Answer

Trigger a change detection by using ChangeDetectorRef in the refresh   method   just after receiving the new data  inject ChangeDetectorRef in the constructor and use detectChanges like this   import   Component  OnInit  ChangeDetectorRef   from   angular core   import   LanguageModel  LANGUAGE DATA   from              models language model   import   LanguageAddComponent   from    language-add language-add component   import   AuthService   from              services auth service   import   LanguageDataSource   from    language-data-source   import   LevelbarComponent   from              directives levelbar levelbar component   import   DataSource   from   angular cdk collections   import   Observable   from  rxjs Observable   import  rxjs add observable of   import   MatSnackBar  MatDialog   from   angular material     Component     selector   app-language     templateUrl     language component html     styleUrls      language component scss      export class LanguageComponent implements OnInit     displayedColumns     name    native    code    level      teachDS  any     user  any     constructor private authService  AuthService  private dialog  MatDialog                private changeDetectorRefs  ChangeDetectorRef         ngOnInit         this refresh           add         this dialog open LanguageAddComponent          data    user  this user           afterClosed   subscribe result   gt          this refresh                   refresh         this authService getAuthenticatedUser   subscribe  res    gt          this user   res        this teachDS   new LanguageDataSource this user profile languages teach         this changeDetectorRefs detectChanges

User · Answer

Since you are using MatPaginator  you just need to do any change to paginator  this triggers data reload   Simple trick   this paginator  changePageSize this paginator pageSize      This updates the page size to the current page size  so basically nothing changes  except the private  emitPageEvent   function is called too  triggeing table reload

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I achieved a good solution using two resources   refreshing both dataSource and paginator   this dataSource data   this users  this dataSource connect   next this users   this paginator  changePageSize this paginator pageSize     where for example dataSource is defined here         users  User                dataSource   new MatTableDataSource this users               this dataSource paginator   this paginator

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In Angular 10  this is what works for me  In the HTML   lt mat-table  dataSource   quot myArray quot  gt   In the component TS      myArray  MyObject           addObjectToTable object MyObject   void           TO PREVENT DUPLICATED OBJECTS     if  object amp  amp   this myArray includes object           this myArray push object            TO FORCE DATA-TABLE s DATASOURCE TO REFRESH       this myArray      this myArray

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So for me  nobody gave the good answer to the problem that i met which is almost the same than  Kay  For me it s about sorting  sorting table does not occur changes in the mat  I purpose this answer since it s the only topic that i find by searching google  I m using Angular 6   As said here      Since the table optimizes for performance  it will not automatically check for changes to the data array  Instead  when objects are added  removed  or moved on the data array  you can trigger an update to the table s rendered rows by calling its renderRows   method    So you just have to call renderRows   in your refresh   method to make your changes appears   See here for integration

User · Answer

There are two ways to do it because Angular Material is inconsistent  and this is very poorly documented  Angular material table won t update when a new row will arrive  Surprisingly it is told it is because performance issues  But it looks more like a by design issue  they can not change  It should be expected for the table to update when new row occurs  If this behavior should not be enabled by default there should be a switch to switch it off    Anyways  we can not change Angular Material  But we can basically use a very poorly documented method to do it   One - if you use an array directly as a source   call table renderRows     where table is ViewChild of the mat-table  Second - if you use sorting and other features  table renderRows   surprisingly won t work  Because mat-table is inconsistent here  You need to use a hack to tell the source changed  You do it with this method   this dataSource data   yourDataSource    where dataSource is MatTableDataSource wrapper used for sorting and other features

User · Answer

In Angular 9  the secret is this dataSource data   this dataSource data   Example   import   MatTableDataSource   from   angular material table    dataSource  MatTableDataSource lt MyObject gt    refresh    void       this applySomeModif           Do what you want with dataSource      this dataSource data   this dataSource data     applySomeModif    void          add some data     this dataSource data push new MyObject            delete index number 4     this dataSource data splice 4  0

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I did some more research and found this place to give me what I needed - feels clean and relates to update data when refreshed from server  https   blog angular-university io angular-material-data-table   Most credits to the page above  Below is a sample of how a mat-selector can be used to update a mat-table bound to a datasource on change of selection  I am using Angular 7  Sorry for being extensive  trying to be complete but concise - I have ripped out as many non-needed parts as possible  With this hoping to help someone else getting forward faster   organization model ts   export class Organization       id  number      name  String      organization service ts   import   Observable  empty   from  rxjs   import   of   from  rxjs    import   Organization   from    organization model    export class OrganizationService     getConstantOrganizations filter  String   Observable lt Organization   gt        if  filter      All           let Organizations  Organization                 id  1234  name   Some data                   return of Organizations          else          let Organizations  Organization                  id  5678  name   Some other data                   return of Organizations                just a sample  other filterings would go here - and of course data instead fetched from server      organizationdatasource model ts   import   CollectionViewer  DataSource   from   angular cdk collections   import   Observable  BehaviorSubject  of   from  rxjs   import   catchError  finalize   from  rxjs operators    import   OrganizationService   from    organization service   import   Organization   from    organization model    export class OrganizationDataSource extends DataSource lt Organization gt      private organizationsSubject   new BehaviorSubject lt Organization   gt          private loadingSubject   new BehaviorSubject lt boolean gt  false      public loading    this loadingSubject asObservable       constructor private organizationService  OrganizationService          super           loadOrganizations filter  String        this loadingSubject next true        return this organizationService getOrganizations filter  pipe        catchError      gt  of             finalize      gt  this loadingSubject next false         subscribe organization   gt  this organizationsSubject next organization           connect collectionViewer  CollectionViewer   Observable lt Organization   gt        return this organizationsSubject asObservable           disconnect collectionViewer  CollectionViewer   void       this organizationsSubject complete        this loadingSubject complete            organizations component html    lt div class  spinner-container   ngIf  organizationDataSource loading    async  gt       lt mat-spinner gt  lt  mat-spinner gt   lt  div gt    lt div gt     lt form  formGroup   formGroup  gt       lt mat-form-field fxAuto gt         lt div fxLayout  row  gt           lt mat-select formControlName  organizationSelectionControl   selectionChange   updateOrganizationSelection    gt             lt mat-option  ngFor  let organizationSelectionAlternative of organizationSelectionAlternatives               value   organizationSelectionAlternative  gt                organizationSelectionAlternative name              lt  mat-option gt           lt  mat-select gt         lt  div gt       lt  mat-form-field gt     lt  form gt   lt  div gt    lt mat-table fxLayout  column   dataSource   organizationDataSource  gt     lt ng-container matColumnDef  name  gt       lt mat-header-cell  matHeaderCellDef gt Name lt  mat-header-cell gt       lt mat-cell  matCellDef  let organization  gt   organization name   lt  mat-cell gt     lt  ng-container gt      lt ng-container matColumnDef  number  gt       lt mat-header-cell  matHeaderCellDef gt Number lt  mat-header-cell gt       lt mat-cell  matCellDef  let organization  gt   organization number   lt  mat-cell gt     lt  ng-container gt      lt mat-header-row  matHeaderRowDef  displayedColumns  gt  lt  mat-header-row gt     lt mat-row  matRowDef  let row  columns  displayedColumns  gt  lt  mat-row gt   lt  mat-table gt    organizations component scss    spinner-container       height  360px      width  390px      position  fixed      organization component ts   import   Component  OnInit   from   angular core   import   FormGroup  FormBuilder   from   angular forms   import   Observable   from  rxjs    import   OrganizationService   from    organization service   import   Organization   from    organization model   import   OrganizationDataSource   from    organizationdatasource model     Component     selector   organizations     templateUrl     organizations component html     styleUrls      organizations component scss      export class OrganizationsComponent implements OnInit     public displayedColumns  string      public organizationDataSource  OrganizationDataSource    public formGroup  FormGroup     public organizationSelectionAlternatives          id  1      name   All             id  2      name   With organization update requests             id  3      name   With contact update requests             id  4      name   With order requests          constructor      private formBuilder  FormBuilder      private organizationService  OrganizationService         ngOnInit         this formGroup   this formBuilder group          organizationSelectionControl                  const toSelect   this organizationSelectionAlternatives find c   gt  c id    1       this formGroup get  organizationSelectionControl   setValue toSelect        this organizationDataSource   new OrganizationDataSource this organizationService       this displayedColumns     name    number         this updateOrganizationSelection           updateOrganizationSelection         this organizationDataSource loadOrganizations this formGroup get  organizationSelectionControl   value name

User · Answer

You can just use the datasource connect function  this datasource connect   next data     like so   data  being the new values for the datatable

[angular] Angular + Material - How to refresh a data source (mat-table)

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