feat(sorting): Sort expression accepts type model for type narrowing (#12991)

Author: rkaraivanov

CHANGELOG.md

@@ -8,7 +8,7 @@ All notable changes for each version of this project will be documented in this
 - All Ignite UI for Angular components are now exported as `standalone` components. The library still exports `NgModules`, which have been preserved for backward compatibility, but they no longer declare any of the Ignite UI for Angular components, instead they just import and export the `standalone` components. The `standalone` components are still in a preview stage. Some utility directive exports may change in the future and may be missing from the documentation in the initial release, hence the `preview` state of the feature.
 
 Now you can do:
-    
+
 ```typescript
 // IGX_GRID_DIRECTIVES exports all grid related components and directives
 import { IGX_GRID_DIRECTIVES } from 'igniteui-angular';
@@ -22,7 +22,7 @@ import { IGX_GRID_DIRECTIVES } from 'igniteui-angular';
 })
 ```
 
-or 
+or
 
 ```typescript
 // Single import of only the <igx-grid> component.
@@ -65,6 +65,7 @@ import { IgxGridModule } from 'igniteui-angular';
 - `IgxGrid`, `IgxHierarchicalGrid`:
     - `totalItemCount` can now also be bound as `Input` in remote virtualization scenarios.
     - `rowExpandedIndicatorTemplate`, `rowCollapsedIndicatorTemplate`, `headerExpandedIndicatorTemplate`, `headerCollapsedIndicatorTemplate` can now also be bound as `Input` to provide templates for the row and header expand/collapse indicators respectively. This is in addition to the existing equivalent template directives to allow reuse.
+- `ISortingExpression` now accepts an optional generic type parameter for type narrowing of the `fieldName` property to keys of the data item, e.g. `ISortingExpression<MyDataItem>`
 
 ## 15.1.0
 

projects/igniteui-angular/src/lib/core/types.ts

@@ -0,0 +1 @@
+export type KeyOfOrString<T, K = keyof T> = K extends keyof T ? K : string;

projects/igniteui-angular/src/lib/data-operations/sorting-strategy.ts

@@ -1,3 +1,4 @@
+import type { KeyOfOrString } from '../core/types';
 import { IBaseEventArgs } from '../core/utils';
 import { GridType } from '../grids/common/grid.interface';
 
@@ -7,8 +8,8 @@ export enum SortingDirection {
     Desc = 2
 }
 
-export interface ISortingExpression extends IBaseEventArgs {
-    fieldName: string;
+export interface ISortingExpression<T = any> extends IBaseEventArgs {
+    fieldName: KeyOfOrString<T> & string;
     dir: SortingDirection;
     ignoreCase?: boolean;
     strategy?: ISortingStrategy;
@@ -124,4 +125,4 @@ export class GroupMemberCountSortingStrategy implements ISortingStrategy {
 
         return reverse * (firstItemValuesLength - secondItemValuesLength);
     }
-}
+}