Angular Data GridColumn State

Column Definitions contain both stateful and non-stateful attributes. Stateful attributes can have their values changed by the grid (e.g. Column sort can be changed by the user clicking on the column header). Non-stateful attributes do not change from what is set in the Column Definition (e.g. once the Header Name is set as part of a Column Definition, it typically does not change).

The full list of stateful attributes of Columns are represented by the ColumnStateParams interface:

This section details how such state items can be manipulated without having to update Column Definitions.

Save and Apply State

There are two API methods provided for getting and setting Column State. columnApi.getColumnState() gets the current column state and columnApi.applyColumnState(params) sets the column state.

// save the column's state
const savedState = this.gridColumnApi.getColumnState(); 

// restore the column state
this.gridColumnApi.applyColumnState({ state: savedState });

The example below demonstrates saving and restoring column state. Try the following:

1. Click 'Save State' to save the Column State.
2. Change some column state e.g. resize columns, move columns around, apply column sorting or row grouping etc.
3. Click 'Restore State' and the column's state is set back to where it was when you clicked 'Save State'.
4. Click 'Reset State' and the state will go back to what was defined in the Column Definitions.

Column State Interface

The Column State method interfaces are as follows:

Partial State

It is possible to focus on particular columns and / or particular attributes when getting and / or applying a Column State. This allows fine grained control over the Column State, e.g. setting what Columns are Pinned, without impacting any other state attribute.

Applying Partial State

When applying a Column State, in cases where some state attributes or columns are missing from the Column State, the following rules apply:

• Attributes that are not supplied or are set to undefined will remain unchanged. For example if a Column has a Column State with just pinned, then Pinned is applied to that Column but other attributes, such as sort are left intact.

• When state is applied and there are additional Columns in the grid that do not appear in the provided state, then the params.defaultState is applied to those additional Columns.

• If params.defaultState is not provided, then any additional Columns in the grid will not be updated.

Combining these rules together leaves for flexible fine grained state control. Take the following code snippets as examples:

// Sort Athlete column ascending
this.gridColumnApi.applyColumnState({
     state: [
         {
             colId: 'athlete',
             sort: 'asc'
         }
     ]
 });

// Sort Athlete column ascending and clear sort on all other columns
this.gridColumnApi.applyColumnState({
     state: [
         {
             colId: 'athlete',
             sort: 'asc'
         }
     ],
     defaultState: {
         // important to say 'null' as undefined means 'do nothing'
         sort: null
     }
 });

// Clear sorting on all columns, leave all other attributes untouched
this.gridColumnApi.applyColumnState({
     defaultState: {
         // important to say 'null' as undefined means 'do nothing'
         sort: null
     }
 });

// Clear sorting, row group, pivot and pinned on all columns, leave all other attributes untouched
this.gridColumnApi.applyColumnState({
     defaultState: {
         // important to say 'null' as undefined means 'do nothing'
         sort: null,
         rowGroup: null,
         pivot: null,
         pinned: null
     }
 });

// Order columns, but do nothing else
this.gridColumnApi.applyColumnState({
     state: [
         { colId: 'athlete' },
         { colId: 'country' },
         { colId: 'age' },
         { colId: 'sport' }
     ],
     applyOrder: true
 });

The example below shows some fine grained access to Column State.

Saving Partial State

Using the techniques above, it is possible to save and restore a subset of the parameters in the state. The example below demonstrates this by selectively saving and restoring a) sort state and b) column visibility and order state.

Note that when saving and restoring Sort state, other state attributes (width, row group, column order etc) are not impacted.

Likewise when saving and restoring visibility and order, only visibility and order will be impacted when re-applying the state.

Considerations

There are a few items to note on specific state attributes. They are as follows:

null vs undefined

For all state attributes, undefined means "do not apply this attribute" and null means "clear this attribute".

For example setting sort=null will clear sort on a column whereas setting sort=undefined will leave whatever sort, if any, that is currently present.

The only exception is with regards to Column Width. For width, both undefined and null will skip the attribute. This is because width is mandatory - there is no such thing as a Column with no width.

Width and Flex

When Flex is active on a Column, the grid ignores the width attribute when setting the width.

When getColumnState() is called, both width and flex are returned. When applyColumnState() is called, if flex is present then width is ignored.

If you want to restore a Column's width to the exact same pixel width as specified in the Column State, set flex=null for that Column's state to turn Flex off.

Row Group and Pivot

There are two attributes representing both Row Group and Pivot. First using the boolean attributes rowGroup and pivot and then secondly using the index attributes rowGroupIndex and pivotIndex.

When getColumnState() is called, all of rowGroup, pivot, rowGroupIndex and pivotIndex are returned. When applyColumnState() is called, preference is given to the index variants. For example if both rowGroup and rowGroupIndex are present, rowGroupIndex is applied.

Column Events

Column Events will get raised when applying a Column State as these events would normally get raised. For example columnPinned event will get raised if applying the state results in a column getting pinned or unpinned.

The example below demonstrates events getting raised based on Column State changes. The example logs event information to the console, so best open the example in a new tab and observe the dev console.

Column Group State

Column Group State is concerned with the state of Column Groups. There is only one state attribute for Column Groups, which is whether the group is open or closed.

To get the state of Column Groups use the API method columnApi.getColumnGroupState(). To set the Column Group state use the API method columnApi.setColumnGroupState(stateItems).

The example below demonstrates getting and setting Column Group State. Note the following:

• Clicking 'Save State' will save the opened / closed state of column groups.
• Clicking 'Restore State' will restore the previously saved state.
• Clicking 'Reset State' will reset the column state to match the Column Definitions,

i.e. all Column Groups will be closed.