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Description

OData Backend Service (for Pagination purposes) to get data from a backend server with the help of OData.

Note

Use it when you need to support Pagination (that is when your dataset is rather large, more than 5k rows) with a OData endpoint. If your dataset is small (less than 5k rows), then go with a regular grid with the "dataset.bind" property. SlickGrid can easily handle million of rows using a DataView object, but personally when the dataset is known to be large, I usually use a backend service (OData or GraphQL) and when it's small I go with a regular grid.

Implementation

To connect a backend service into Slickgrid-Universal, you simply need to modify your gridOptions and add a declaration of backendServiceApi and pass it the service. See below for the signature and an example further down below.

Demo

Demo Page / Demo ViewModel

IMPORTANT NOTE

All the code below assumes that your Backend Server (probably in C#) will return the data into an items property. You could return the array directly but it is strongly discouraged to do that because that will conflict with the metrics that you will see in the code below. The best approach is to return your data into a property, like items or any property name you wish to use, on your backend server side. Your result should have this kind of structure

{
  items: [ /* your data */ ]
}

TypeScript Signature

backendServiceApi: {
  // Backend Service instance (could be OData or GraphQL Service)
  service: BackendService;

  // add any options you might want to provide to the backend service
  options: OdataOption | GraphqlServiceOption;

  // On init (or on page load), what action to perform?
  onInit?: (query: string) => Promise<any>;

  // Before executing the query, what action to perform? For example, start a spinner
  preProcess?: () => void;

  // On Processing, we get the query back from the service, and we need to provide a Promise. For example: this.http.get(myGraphqlUrl)
  process: (query: string) => Promise<any>;

  // After executing the query, what action to perform? For example, stop the spinner
  postProcess: (response: any) => void;

  // Throttle the amount of requests sent to the backend. Default to 500ms
  filterTypingDebounce?: number;
}

As you can see, you mainly need to define which service to use (GridODataService or GraphQLService) and finally add the process and postProcess callback.

Grid Definition & call of backendServiceApi

Notes

  • Pagination is optional and if not defined, it will use what is set in the Slickgrid-Universal - Global Options

  • onInit is optional and is there to initialize (pre-populate) the grid with data on first page load (typically the same call as process)

    • you could load the grid yourself outside of the gridOptions which is why it's optional

  • filterTypingDebounce is a timer (in milliseconds) that waits for user input pause before querying the backend server

    • this is meant to throttle the amount of requests sent to the backend (we don't really want to query every keystroke)

    • 700ms is the default when not provided

Code

import { GridOdataService, OdataServiceApi, OdataOption } from '@slickgrid-universal/odata';

export class Example {
  columnDefinitions: Column[];
  gridOptions: GridOption;
  dataset = [];

  constructor(http) {
    this.http = http;

    // define the grid options & columns and then create the grid itself
    this.defineGrid();
  }

  defineGrid() {
    this.columnDefinitions = [
      // your column definitions
    ];

    this.gridOptions = {
      enableFiltering: true,
      enablePagination: true,
      pagination: {
        pageSizes: [10, 15, 20, 25, 30, 40, 50, 75, 100],
        pageSize: defaultPageSize,
        totalItems: 0
      },
      backendServiceApi: {
        service: new GridOdataService(),
        // define all the on Event callbacks
        options: {
          caseType: CaseType.pascalCase,
          top: defaultPageSize
        } as OdataOption,
        preProcess: () => this.displaySpinner(true),
        process: (query) => this.getCustomerApiCall(query),
        postProcess: (response) => {
          this.displaySpinner(false);
          this.getCustomerCallback(response);
        }
      }
    };
  }

  // Web API call
  getCustomerApiCall(odataQuery) {
    // regular Http Client call
    return this.http.createRequest(`/api/customers?${odataQuery}`).asGet().send().then(response => response.content);

    // or with Fetch Client
    // return this.http.fetch(`/api/customers?${odataQuery}`).then(response => response.json());
  }

  getCustomerCallback(response) {
    // totalItems property needs to be filled for pagination to work correctly
    // however we need to force the Framework to do a dirty check, doing a clone object will do just that
    let countPropName = 'totalRecordCount'; // you can use "totalRecordCount" or any name or "odata.count" when "enableCount" is set
    if (this.isCountEnabled) {
      countPropName = (this.odataVersion === 4) ? '@odata.count' : 'odata.count';
    }
    if (this.metrics) {
      this.metrics.totalItemCount = data[countPropName];
    }

    // once pagination totalItems is filled, we can update the dataset
    this.sgb.paginationOptions.totalItems = data[countPropName];
    this.sgb.dataset = data.items as Customer[];
  }
}

Passing Extra Arguments to the Query

You might need to pass extra arguments to your OData query, for example passing a userId, you can do that simply by modifying the query you sent to your process callback method. For example

// Web API call
getCustomerApiCall(odataQuery) { with Fetch Client
  const finalQuery = `${odataQuery}$filter=(userId eq 12345)`;
  return this.http.get(`/api/getCustomers?${finalQuery}`);
}

OData options

All options can be found here: Slickgrid-Universal - OData Options

Some are described in more detail below.

OData version

By default the OData version is set to 2 because it was implemented with that version. If you wish to use version 4, then just change the version: 4, there are subtle differences.

this.gridOptions = {
  backendServiceApi: {
    service: new GridOdataService(),
      options: {
        enableCount: true, // add the count in the OData query, which will return a property named "odata.count" (v2) or "@odata.count" (v4)
        version: 4        // defaults to 2, the query string is slightly different between OData 2 and 4
      } as OdataOption,
      process: (query) => this.getCustomerApiCall(query),
      postProcess: (response) => {
        this.metrics = response.metrics;
        this.displaySpinner(false);
        this.getCustomerCallback(response);
      }
  } as OdataServiceApi
};

Query total items count

The total items count can be queried from the backend by:

const oDataOptions: OdataOption = {
  enableCount: true;
}

When enabled that will add $inlinecount=allpages (v2/v3) or $count=true (v4) to the query. And the count from the backend's response is extracted and pagination.totalItems is updated with that count. The property in the response that is used depends on the oData version specified: d.__count for v2, __count for v3 and @odata.count for v4. If needed a custom extractor function can be set through oDataOptions.countExtractor.

Query only the grid column's fields

Query only the grid column's fields from the backend by:

const oDataOptions: OdataOption = {
  enableSelect: true;
}

For example columns: [{ id: 'col1', field: 'field1' }, { id: 'col2', field: 'field2' }] results in the query: ?$select=id,field1,field2.

A property id is always selected from the backend because the grid requires it. This property can be changed by setting gridOptions.datasetIdPropertyName.

Query related resources / expand navigation properties

Specify that related resources (navigation properties) should be retrieved from the backend:

const oDataOptions: OdataOption = {
  enableExpand: true;
}

A navigation property is identified as a field having / in it's name. For example columns: [{ id: 'col1', field: 'nav1/field1' }, { id: 'col2', field: 'nav2/field1' }] results in the query ?$expand=nav1,nav2

Often enableSelect and enableExpand are used in conjunction. And with oData v4 then also navigation properties are selected from the backend. For example columns: [{ id: 'col1', field: 'nav1/field1' }, { id: 'col2', field: 'nav2/field1' }] results in the query ?$select=id,$expand=nav1($select=field1),nav2($select=field2)

const oDataOptions: OdataOption = {
  enableSelect: true;
  enableExpand: true;
  version: 4
}

Navigations within navigations are also supported. For example columns: [{ id: 'col1', field: 'nav1/subnav1/field1' }].

The dataset from the backend is automatically extracted and navigation fields are flattened so the grid can display them and sort/filter just work. The exact property that is used as the dataset depends on the oData version: d.results for v2, results for v3 and value for v4. If needed a custom extractor function can be set through oDataOptions.datasetExtractor. For example if the backend responds with { value: [{ id: 1, nav1: { field1: 'x' }, { nav2: { field2: 'y' } } ] } this will be flattened to { value: [{ id: 1, 'nav1/field1': 'x', 'nav2/field2': 'y' } ] }.

Override the filter query

Column filters may have a Custom operator, that acts as a placeholder for you to define your own logic. To do so, the easiest way is to provide the filterQueryOverride callback in the OdataOptions. This method will be called with BackendServiceFilterQueryOverrideArgs to let you decide dynamically on how the filter should be assembled.

E.g. you could listen for a specific column and the active OperatorType.custom in order to switch the filter to a matchesPattern SQL LIKE search:

backendServiceApi: {
  options: {
    filterQueryOverride: ({ fieldName, columnDef, columnFilterOperator, searchValues }) => {
      if (columnFilterOperator === OperatorType.custom && columnDef?.id === 'name') {
        let matchesSearch = searchValues[0].replace(/\*/g, '.*');
        matchesSearch = matchesSearch.slice(0, 1) + '%5E' + matchesSearch.slice(1);
        matchesSearch = matchesSearch.slice(0, -1) + '$\'';

        return `matchesPattern(${fieldName}, ${matchesSearch})`;
      }
    },
  }
}
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