# Grid State & Presets

**index**

* [Description](#descriptions)
* [Grid State](#grid-state-1)
* [Grid Presets](#grid-presets)
* [Grid State Events](#grid-state-events)
* [How to Load Grid with Certain Columns Hidden](#how-to-load-grid-with-certain-columns-preset-example-hide-certain-columns-on-load)

#### Demo

Look at your developer console before leaving the page

**Regular grid**

[Demo Page](https://ghiscoding.github.io/angular-slickgrid-demos/#/clientside) / [Demo Component](https://github.com/ghiscoding/slickgrid-universal/blob/master/frameworks/angular-slickgrid/src/demos/examples/grid-clientside.component.ts)

**with Backend Service**

[Demo Page](https://ghiscoding.github.io/angular-slickgrid-demos/#/gridgraphql) / [Demo Component](https://github.com/ghiscoding/slickgrid-universal/blob/master/frameworks/angular-slickgrid/src/demos/examples/grid-graphql.component.ts)

### Descriptions

**Grid State**

The `Grid State` are what we defined as the currently used `Columns` / `Filters` / `Sorters` / `Pagination` of the actual grid (pagination is only returned when used with Backend Service API). The columns also include their (size, position order & visibility (show/hidden)).

**Presets**

Presets can be used to preset a grid with certain `Columns` / `Filters` / `Sorters` / `Pagination`. When we say `Columns`, we actually mean their size, order position and visibility (shown/hidden) in the grid.

**Combining the two together**

So basically, the idea is to save the `Grid State` in Local Storage (or DB) before the grid gets destroyed and once we come back to that same page we can preset the grid with the exact same state as it was before leaving the page (just like if we were doing a forward/back button with browser history).

### Grid State

You can get the `Grid State` at any point in time. However if you wish to save the grid state before leaving the page and store that in Local Storage, then the best way is to use the `onBeforeGridDestroy` Event Emitter.

**View**

```html
<angular-slickgrid
     gridId="grid2"
     [columns]="columnDefinitions"
     [options]="gridOptions"
     [dataset]="dataset"
     (onAngularGridCreated)="angularGridReady($event.detail)"
     (onBeforeGridDestroy)="saveCurrentGridState($event)">
</angular-slickgrid>
```

**Component**

```typescript
import { GridState } from 'angular-slickgrid';

@Component({
  templateUrl: './grid-demo.component.html'
})
export class GridDemoComponent {
  angularGrid: AngularGridInstance;

  angularGridReady(angularGrid: AngularGridInstance) {
    this.angularGrid = angularGrid;
  }

  // you can save it to Local Storage of DB in this call
  saveCurrentGridState(grid) {
    const gridState: GridState = this.angularGrid.gridStateService.getCurrentGridState();
    console.log('Leaving page with current grid state', gridState);
  }
}
```

#### Using Grid Presets & Filter SearchTerm(s)

What happens when we use the grid `presets` and a [Filter Default SearchTerms](../../column-functionalities/filter-intro/select-filter#default-search-terms)? In this case, the `presets` will win over filter `searchTerms`. The cascading order of priorities is the following

1. Do we have any `presets`? Yes use them, else go to step 2
2. Do we have any Filter `searchTerms`? Yes use them, else go to step 3
3. No `presets` and no `searchTerms`, load grid with default grid & column definitions

### Grid Presets

#### Structure

The current structure of a Grid Presets is the following

```typescript
export interface CurrentColumn {
  columnId: string;
  cssClass?: string;
  headerCssClass?: string;
  width?: number;
}
export interface CurrentFilter {
  columnId: string;
  operator?: OperatorType | OperatorString;
  searchTerms?: SearchTerm[];
}
export interface CurrentSorter {
  columnId: string;
  direction: SortDirection | SortDirectionString;
}
export interface GridState {
  columns?: CurrentColumn[] | null;
  filters?: CurrentFilter[] | null;
  sorters?: CurrentSorter[] | null;
  pagination?: {
    pageNumber: number;
    pageSize: number;
  };
  pinning?: CurrentPinning;
  rowSelection?: CurrentRowSelection | null;
  treeData?: Partial<TreeToggleStateChange> | null;
}
```

> \[!NOTE] You can get Grouping column Ids as Grid State but it is limited to Draggable Grouping **only** via Grid Presets and it will not work with regular Grouping.

**Example**

For example, we can set `presets` on a grid like so: **Component**

```typescript
import { GridState } from 'angular-slickgrid';

@Component({
  templateUrl: './grid-demo.component.html'
})
export class GridDemoComponent {
  angularGrid: AngularGridInstance;

  ngOnInit(): void {
    this.columnDefinitions = [
      { id: 'name', name: 'Name', field: 'name', filterable: true, sortable: true, sortable: true },
      { id: 'duration', name: 'Duration', field: 'duration', filterable: true, sortable: true },
      { id: 'complete', name: '% Complete', field: 'percentComplete', filterable: true, sortable: true },
    ];

    this.gridOptions = {
      enableFiltering: true,

      // use columnDef searchTerms OR use presets as shown below
      presets: {
        // the column position in the array is very important and represent
        // the position that will show in the grid
        columns: [
          { columnId: 'duration', width: 88, headerCssClass: 'customHeaderClass' },
          { columnId: 'complete', width: 57 }
        ],
        filters: [
          { columnId: 'duration', searchTerms: [2, 22, 44] },
          { columnId: 'complete', searchTerms: ['>5'] }
        ],
        sorters: [
          { columnId: 'duration', direction: 'DESC' },
          { columnId: 'complete', direction: 'ASC' }
        ],

        // with Backend Service ONLY, you can also add Pagination info
        pagination: { pageNumber: 2, pageSize: 20 }
      }
    };
}
```

#### Grid State Event

There are 2 ways of subscribing to GridState Service event changed.

1. Through `(onGridStateChanged)` Event Emitter (recommended)
2. Through `onGridStateChanged` Observable on the GridState Service.

Examples

**1. `(onGridStateChanged)` Event Emitter (recommended)**

**View**

```html
<angular-slickgrid gridId="grid1"
         [columns]="columnDefinitions"
         [options]="gridOptions"
         [dataset]="dataset"
         (onGridStateChanged)="gridStateChanged($event)">
</angular-slickgrid>
```

**Component**

```typescript
import { GridStateChange } from 'angular-slickgrid';

export class ExampleComponent implements OnInit {
  gridStateChanged(gridState: GridStateChange) {
    console.log('Grid State changed:: ', gridState);
  }
}
```

**2. Through `onGridStateChanged` Observable on the GridState Service**

**View**

```html
<angular-slickgrid
     gridId="grid2"
     [columns]="columnDefinitions"
     [options]="gridOptions"
     [dataset]="dataset"
     (onAngularGridCreated)="angularGridReady($event.detail)"
     (onBeforeGridDestroy)="saveCurrentGridState($event)">
</angular-slickgrid>
```

**Component**

```typescript
import { AngularGridInstance, GridStateChange } from 'angular-slickgrid';

export class ExampleComponent implements OnInit, OnDestroy {
  angularGrid: AngularGridInstance;
  gridStateSub: Subscription;

  angularGridReady(angularGrid: AngularGridInstance) {
    this.angularGrid = angularGrid;
    this.gridStateSub = this.angularGrid.gridStateService.onGridStateChanged.subscribe((data: GridStateChange) => console.log(data));
  }

  ngOnDestroy() {
    this.gridStateSub.unsubscribe();
  }
}
```

### How to Load Grid with certain Columns Preset (example hide certain Column(s) on load)

You can show/hide or even change a column position via the `presets`, yes `presets` is that powerful. All you need to do is to pass all Columns that you want to show as part of the `columns` property of `presets`. Typically you already have the entire columns definition since you just defined it, so you can loop through it and just use `map` to list the `columns` according to the structure needed (see [preset structure](https://github.com/ghiscoding/slickgrid-universal/blob/master/frameworks/angular-slickgrid/docs/grid-functionalities/grid-state-preset/README.md#structure.md)). What you have to know is that whatever array you provide to `presets`, that will equal to what the user will see and also in which order the columns will show (the array order does matter in this case). If a Columns is omitted from that array, then it will be considered to be a hidden column (you can still show it through Grid Menu and/or Column Picker).

So let say that we want to hide the last Column on page load, we can just find the column by it's `id` that you want to hide and pass the new column definition to the `presets` (again make sure to follow the correct preset structure).

```ts
this.columnDefinitions = [
  // initial column definitions
];

// for example, let's hide last column, we can just use `pop()` to ommit last column
// and use `map()` to pull only the required field for presets to work
const mappedColumnDefinitions = this.columnDefinitions.map(col => ({ columnId: col.id, width: col.width }));
mappedColumnDefinitions.pop();

// then pass it to the presets
this.gridOptions = {
  presets: {
    columns: mappedColumnDefinitions
  }
};
```

This would be the easiest way to do it.

As pointed out earlier, the `presets` requires a specific structure where the `columns` is the list of columns to show/hide with their possible widths. Also worth mentioning again that the position in the array is very important as it defines the position shown in the UI.

```ts
this.gridOptions = {
      enableFiltering: true,

      // use columnDef searchTerms OR use presets as shown below
      presets: {
        // the column position in the array is very important and represent
        // the position that will show in the grid
        columns: [
          { columnId: 'duration', width: 88, headerCssClass: 'customHeaderClass' },
          { columnId: 'complete', width: 57 }
        ],
   }
};
```

You could technically redefine by hand the complete list of `columns` that the `presets` requires. I would personally do it via the Column Definitions looping with `map()`, but go manual is also perfectly fine. You would just re-declare the `columns` again with the `id` and `width` and that would work as well.
