# Wijmo.Collectionview ## Content

CollectionView Class

Class that implements the ICollectionView interface to expose data in regular JavaScript arrays.

The CollectionView class implements the following interfaces:

To use the CollectionView class, start by declaring it and passing a regular array as a data source. Then configure the view using the filter, sortDescriptions, groupDescriptions, and pageSize properties. Finally, access the view using the items property. For example:

import { CollectionView, SortDescription} from '@mescius/wijmo';

// create a CollectionView based on a data array
let view = new CollectionView(dataArray);

// sort items by amount in descending order
let sortDesc = new SortDescription('amount', false);
view.sortDescriptions.push(sortDesc);

// show only items with amounts greater than 100
view.filter = (item) => { return item.amount > 100 };

// show the sorted, filtered result on the console
view.items.forEach((item, index) => {
    console.log(index + ': ' + item.name + ' ' + item.amount);
});

The example below shows how you can use a CollectionView to provide sorted views of some raw data:

Example

Type parameters

Heirarchy

Constructors

Properties

Methods

Events

Constructors

constructor

  • new CollectionView(sourceCollection?: Array<Partial<T> | T>, options?: any): CollectionView

  • Initializes a new instance of the CollectionView class.

    Parameters

    • Optional sourceCollection: Array<Partial<T> | T>

      Array that serves as a source for this CollectionView.

    • Optional options: any

      JavaScript object containing initialization data for the control.

    Returns CollectionView

Properties

calculatedFields

calculatedFields: any

Gets or sets an object where the keys represent calculated fields and the values are expressions (functions or strings).

Calculated fields require proxies. To use them in IE11, you will need a polyfill such as this one: https://www.npmjs.com/package/proxy-polyfill.

Calculated fields can be useful when dealing with external data. For example, you could add a per-capita income field (gnp/pop) or a profit field (revenue-expenses).

Calculated fields are dynamic. If you change the fields used in the calculation, their values are updated automatically. They are also read-only. You may change the value of the properties used to calculate them, but you cannot directly edit the result.

Unlike FlexGrid cellTemplates, calculated fields can be used for sorting, filtering, and grouping. They can also be used with charts and any other Wijmo controls.

Calculated fields can be defined as functions that take a data item as an argument or as strings.

For example, if your data looked like this:

// regular data item
interface IDataItem {
      product: string,
      brand: string,
      unitPrice: number,
      qty: number,
      shipped: boolean
}
function getData(): IDataItem[] {
    return [
        {
            product: 'Banana',
            brand: 'Chiquita',
            unitPrice: 45.95,
            qty: 12,
            discount: .08,
            shipped: true
        }, ...
    ]
}

You could add function-based calculated fields this way:

// add calculated properties to IDataItem
interface ICalcDataItem extends IDataItem {
    fullName: string;
    allCaps: string;
    totalPrice: number,
    tax: number;
}

let cv = new CollectionView<ICalcDataItem>(getData(), {
    calculatedFields: {
        fullName: ($: ICalcDataItem) => [$.brand, $.product].join(' '),
        allCaps: ($: ICalcDataItem) => $.fullName.toUpperCase(),
        totalPrice: ($: ICalcDataItem) => ($.unitPrice * $.qty) * (1 - $.discount),
        tax: ($: ICalcDataItem) => $.totalPrice * 0.12
    }
});

Function-based calculated fields are usually a better choice than string-based calculated fields because:

1) They provide design-time error checking and command completion, 2) They run faster, and 3) They do not have any issues with content-security policy (CSP).

Alternatively, you could add string-based calculated fields:

let cv = new CollectionView<IDataItem>(getData(), {
  calculatedFields: {
    fullName: '[$.brand, $.product].join(" ")',
    allCaps: '$.fullNameStr.toUpperCase()',
    totalPrice: '($.unitPrice * $.qty) * (1 - $.discount)',
    tax: '$.totalPrice * 0.12'
});

String expressions may refer to the current item via the context variable '$', which contains the item's original and calculated values.

String-based calculated fields have advantages over function-based calculated fields that may be important in some scenarios:

1) They are slightly more concise, and 2) They can be stored as data and easily changed at run-time.

canAddNew

canAddNew: boolean

Gets a value that indicates whether a new item can be added to the collection.

canCancelEdit

canCancelEdit: boolean

Gets a value that indicates whether the collection view can discard pending changes and restore the original values of an edited object.

canChangePage

canChangePage: boolean

Gets a value that indicates whether the pageIndex value can change.

canFilter

canFilter: boolean

Gets a value that indicates whether this view supports filtering via the filter property.

This property does not affect the filters property, which are always applied.

canGroup

canGroup: boolean

Gets a value that indicates whether this view supports grouping via the groupDescriptions property.

canRemove

canRemove: boolean

Gets a value that indicates whether items can be removed from the collection.

canSort

canSort: boolean

Gets a value that indicates whether this view supports sorting via the sortDescriptions property.

currentAddItem

currentAddItem: Partial<T> | T

Gets the item that is being added during the current add transaction.

currentEditItem

currentEditItem: T

Gets the item that is being edited during the current edit transaction.

currentItem

currentItem: T | object & any

Gets or sets the current item in the view.

currentPosition

currentPosition: number

Gets the ordinal position of the current item in the view.

filter

filter: IPredicate | null

Gets or sets a callback used to determine if an item is suitable for inclusion in the view.

The callback should return true if the item passed in as a parameter should be included in the view.

The default value for this property is null, which means the data is not filtered.

filters

filters: ObservableArray<IPredicate>

Gets an array of {@link IPredicate} functions used as filters on this CollectionView.

To be included in the view, an item has to pass the predicate in the filter property as well as all predicates in the filters collection.

getError

getError: IGetError | null

Gets or sets a callback that determines whether a specific property of an item contains validation errors.

The method takes as parameters a data item, the property being validated, and a parsing parameter that describes whether the data has already been parsed and applied to the data item (parsing == false), or whether the user was trying to edit the value and entered a value that could not be parsed into the data type expected (parsing == true).

The method returns a string containing an error message, or null if no errors were detected.

For example,

view = new CollectionView(data, {
    getError: (item: any, prop: string, parsing: boolean) => {

        // parsing failed, show message
        if (parsing) {
            if (prop == 'date') {
                return 'Please enter a valid date in the format "MM/dd/yyyy"';
            } else if (prop == 'id') {
                return 'Please enter a positive number';
            }
        }

        // check that stored (parsed) data is valid
        if (prop == 'date' && item.date < minDate) {
            return 'Please enter a date after ' + Globalize.formatDate(minDate, 'd');
        } else if (prop == 'id' && item.id < 0) {
            return 'Please enter a positive number';
        }
    }
});

groupDescriptions

groupDescriptions: ObservableArray<GroupDescription>

Gets a collection of GroupDescription objects that describe how the items in the collection are grouped in the view.

groups

groups: CollectionViewGroup[]

Gets an array of CollectionViewGroup objects that represents the top-level groups.

isAddingNew

isAddingNew: boolean

Gets a value that indicates whether an add transaction is in progress.

isEditingItem

isEditingItem: boolean

Gets a value that indicates whether an edit transaction is in progress.

isEmpty

isEmpty: boolean

Gets a value that indicates whether this view contains no items.

isPageChanging

isPageChanging: boolean

Gets a value that indicates whether the page index is changing.

isUpdating

isUpdating: boolean

Gets a value that indicates whether notifications are currently suspended (see beginUpdate and endUpdate).

itemCount

itemCount: number

Gets the total number of items in the view taking paging into account.

items

items: (T | object)[]

Gets items in the view.

itemsAdded

itemsAdded: ObservableArray<Partial<T> | T>

Gets an ObservableArray containing the records that were added to the collection since trackChanges was enabled.

itemsEdited

itemsEdited: ObservableArray<Partial<T> | T>

Gets an ObservableArray containing the records that were edited in the collection since trackChanges was enabled.

itemsRemoved

itemsRemoved: ObservableArray<Partial<T> | T>

Gets an ObservableArray containing the records that were removed from the collection since trackChanges was enabled.

newItemCreator

newItemCreator: IItemCreator<T>

Gets or sets a function that creates new items for the collection.

If the creator function is not supplied, the CollectionView will try to create an uninitialized item of the appropriate type.

If the creator function is supplied, it should be a function that takes no parameters and returns an initialized object of the proper type for the collection.

newItemIndex

newItemIndex: number

Gets or sets the zero-based index that FlexGrid's new row template uses when inserting new items.

The index is honored only when sorting, filtering, and grouping are inactive. With paging enabled, values in the range 0..pageSize - 1 map to positions within the current page; values less than zero or greater than or equal to the current pageSize keep the original addNew behavior and append the item to the end of the sourceCollection. When paging is disabled, non-negative values are treated as positions within the full sourceCollection.

example

// Use the original addNew behavior (append to sourceCollection) cv.newItemIndex = -1;

// Insert at the top of the current page cv.newItemIndex = 0;

// Insert at the bottom of the current page cv.newItemIndex = cv.pageSize - 1;

pageCount

pageCount: number

Gets the total number of pages.

pageIndex

pageIndex: number

Gets the zero-based index of the current page.

pageSize

pageSize: number

Gets or sets the number of items to display on each page.

The default value for this property is zero, which disables paging.

refreshOnEdit

refreshOnEdit: boolean

Gets or sets a value that determines whether the CollectionView should automatically refresh its results (by applying the sort, filter, and grouping operations) after items are edited.

The default value for this property is true, which ensures the collection is always sorted, filtered, and grouped correctly after any edit operations.

Set it to false if you want updates to be deferred when items are edited. In this case, the collection will not be refreshed until the sorting, filtering, and grouping criteria change or until the refresh method is called (Excel behavior).

sortComparer

sortComparer: IComparer<T>

Gets or sets a function used to compare values when sorting.

If provided, the sort comparer function should take as parameters two values of any type, and should return -1, 0, or +1 to indicate whether the first value is smaller than, equal to, or greater than the second. If the sort comparer returns null, the standard built-in comparer is used.

This sortComparer property allows you to use custom comparison algorithms that in some cases result in sorting sequences that are more consistent with user's expectations than plain string comparisons.

For example, see Dave Koele's Alphanum algorithm. It breaks up strings into chunks composed of strings or numbers, then sorts number chunks in value order and string chunks in ASCII order. Dave calls the result a "natural sorting order".

The example below shows a typical use for the sortComparer property:

import { CollectionView, isString } from '@mescius/wijmo';

// create a CollectionView with a custom sort comparer
const view = new CollectionView(data, {
    sortComparer: (a: any, b: any) => {
        return isString(a) && isString(b)
            ? alphanum(a, b) // use custom comparer for strings
            : null; // use default comparer for everything else
    }
});

The example below shows how you can use an Intl.Collator to control the sort order:

import { CollectionView, isString } from '@mescius/wijmo';

// create a CollectionView that uses an Intl.Collator to sort
const collator = window.Intl ? new Intl.Collator() : null;
let view = new CollectionView(data, {
    sortComparer: (a, b) => {
        return isString(a) && isString(b) && collator
            ? collator.compare(a, b) // use collator for strings
            : null; // use default comparer for everything else
    }
});

sortConverter

sortConverter: ISortConverter

Gets or sets a function used to convert values when sorting.

If provided, the function should take as parameters a SortDescription, a data item, and a value to convert, and should return the converted value.

This property provides a way to customize sorting. For example, the FlexGrid control uses it to sort mapped columns by display value instead of by raw value.

For example, the code below causes a CollectionView to sort the 'country' property, which contains country code integers, using the corresponding country names:

const countries = 'US,Germany,UK,Japan,Italy,Greece'.split(',');
view.sortConverter = (sd: SortDescription, item: any, value: any) => {
    return sd.property === 'countryMapped'
        ? countries[value]; // convert country id into name
        : value;
}

The next example combines two values so when sorting by country, the view will break ties by city:

view.sortConverter: (sd: SortDescription, item: any, value: any) => {
    if (sd.property == 'country') {
        value = item.country + '\t' + item.city;
    }
    return value;
}

sortDescriptions

sortDescriptions: ObservableArray<SortDescription>

Gets an array of SortDescription objects that describe how the items in the collection are sorted in the view.

sortNulls

sortNulls: SortNulls

Gets or sets a value that determines how null values should be sorted.

This property is set to SortNulls.Last by default, which causes null values to appear last on the sorted collection, regardless of sort direction. This is also the default behavior in Excel.

sourceCollection

sourceCollection: (T | object)[]

Gets or sets the underlying (unfiltered and unsorted) collection.

totalItemCount

totalItemCount: number

Gets the total number of items in the view before paging is applied.

trackChanges

trackChanges: boolean

Gets or sets a value that determines whether the control should track changes to the data.

The default value for this property is false, so the CollectionView does not keep track of which data items have changed.

If you set this property to true, the CollectionView will keep track of changes to the data and will expose them through the itemsAdded, itemsRemoved, and itemsEdited collections.

Tracking changes is useful in situations where you need to update the server after the user has confirmed that the modifications are valid.

After committing or cancelling changes, use the clearChanges method to clear the itemsAdded, itemsRemoved, and itemsEdited collections.

The CollectionView only tracks changes made when the proper CollectionView methods are used (editItem/commitEdit, addNew/commitNew, and remove). Changes made directly to the data are not tracked.

useStableSort

useStableSort: boolean

Gets or sets whether to use a stable sort algorithm.

Stable sorting algorithms maintain the relative order of records with equal keys. For example, consider a collection of objects with an "Amount" field. If you sort the collection by "Amount", a stable sort will keep the original order of records with the same Amount value.

The default value for this property is false, which causes the CollectionView to use JavaScript's built-in sort method, which is fast and usually stable.

Chrome provides stable sorting since version 70, and Firefox since version 3. As of ES2019, sort is required to be stable. In ECMAScript 1st edition through ES2018, it was allowed to be unstable.

Setting the useStableSort property to true ensures stable sorts on all browsers (even IE 11), but increases sort times by 30% to 50%.

Methods

addNew

  • addNew(item?: Partial<T> | T, commit?: boolean): Partial<T> | T

  • Adds a new item to the collection.

    Calling this methods without any parameters creates a new item, adds it to the collection, and defers refresh operations until the new item is committed using the commitNew method or canceled using the cancelNew method.

    The code below shows how the addNew method is typically used:

    // create the new item, add it to the collection
var newItem = view.addNew();

// initialize the new item
newItem.id = getFreshId();
newItem.name = 'New Customer';

// commit the new item so the view can be refreshed
view.commitNew();

    You can also add new items by pushing them into the sourceCollection and then calling the refresh method. The main advantage of addNew is in user-interactive scenarios (like adding new items in a data grid), because it gives users the ability to cancel the add operation. It also prevents the new item from being sorted or filtered out of view until the transaction is committed.

    New items are empty objects by default, unless the colletion has calculatedFields, in which case the new items will have properties set to values that depend on their data types (empty strings for string properties, zero for numeric properties, and null for other data types).

    This behavior is convenient since in many cases the calculated fields depend on expressions that rely on strings not being null. But you can customize this behavior by setting the newItemCreator property to a function that creates the new items and initializes them in any way you want.

    Parameters

    • Optional item: Partial<T> | T

      Item to be added to the collection (optional).

    • Optional commit: boolean

      Whether to commit the new item immediately.

    Returns Partial<T> | T

    The item that was added to the collection, or null if the transaction failed.

beginUpdate

  • beginUpdate(): void

cancelEdit

  • cancelEdit(): void

cancelNew

  • cancelNew(): void

clearChanges

  • clearChanges(): void

  • Clears all changes by removing all items in the itemsAdded, itemsRemoved, and itemsEdited collections.

    Call this method after committing changes to the server or after refreshing the data from the server.

    Returns void

commitEdit

  • commitEdit(): void

commitNew

  • commitNew(): void

contains

  • contains(item: T): boolean

  • Returns a value indicating whether a given item belongs to this view.

    Parameters

    • item: T

      Item to seek.

    Returns boolean

deferUpdate

  • deferUpdate(fn: Function, force?: boolean): void

  • Executes a function within a beginUpdate/endUpdate block.

    The collection will not be refreshed until the function finishes.

    The deferUpdate method ensures endUpdate is called even if the update function throws an exception.

    Parameters

    • fn: Function

      Function to be executed without updates.

    • Optional force: boolean

      Whether to force a refresh when ending the update.

    Returns void

editItem

  • editItem(item: T): void

endUpdate

  • endUpdate(force?: boolean): void

  • Resume refreshes suspended by a call to beginUpdate.

    Parameters

    • Optional force: boolean

      Whether to force a refresh when ending the update.

    Returns void

getAggregate

  • getAggregate(aggType: Aggregate, binding: string, currentPage?: boolean): any

  • Calculates an aggregate value for the items in this collection.

    Parameters

    • aggType: Aggregate

      Type of aggregate to calculate.

    • binding: string

      Property to aggregate on.

    • Optional currentPage: boolean

      Whether to include only items on the current page.

    Returns any

    The aggregate value.

implementsInterface

  • implementsInterface(interfaceName: string): boolean

  • Returns true if this object supports a given interface.

    Parameters

    • interfaceName: string

      Name of the interface to look for.

    Returns boolean

insertAt

  • insertAt(index: number, item?: Partial<T> | T, commit?: boolean): Partial<T> | T

  • Adds a new item to the collection at the specified position.

    This method is similar to addNew, but allows you to control where the new item is inserted. With paging enabled, values in the range 0..pageSize - 1 map to positions within the current page. Values less than zero or greater than or equal to the current pageSize are ignored. When sorting, filtering, or grouping is active, valid indexes fall back to the original addNew behavior and append items to the end of the sourceCollection. When paging is disabled, non-negative values are treated as positions within the full sourceCollection.

    Parameters

    • index: number

      Zero-based position where the new item should be inserted.

    • Optional item: Partial<T> | T

      Item to be added to the collection (optional).

    • Optional commit: boolean

      Whether to commit the new item immediately.

    Returns Partial<T> | T

    The item that was added to the collection, or null if the transaction failed.

moveCurrentTo

  • moveCurrentTo(item: Partial<T> | T): boolean

  • Sets the specified item to be the current item in the view.

    Parameters

    • item: Partial<T> | T

      Item that will become current.

    Returns boolean

moveCurrentToFirst

  • moveCurrentToFirst(): boolean

moveCurrentToLast

  • moveCurrentToLast(): boolean

moveCurrentToNext

  • moveCurrentToNext(): boolean

moveCurrentToPosition

  • moveCurrentToPosition(index: number): boolean

  • Sets the item at the specified index in the view as the current item.

    Parameters

    • index: number

      Index of the item that will become current.

    Returns boolean

moveCurrentToPrevious

  • moveCurrentToPrevious(): boolean

moveToFirstPage

  • moveToFirstPage(): boolean

moveToLastPage

  • moveToLastPage(): boolean

moveToNextPage

  • moveToNextPage(): boolean

moveToPage

  • moveToPage(index: number): boolean

  • Moves to the page at the specified index.

    Parameters

    • index: number

      Index of the page to move to.

    Returns boolean

    True if the page index was changed successfully.

moveToPreviousPage

  • moveToPreviousPage(): boolean

onCollectionChanged

onCurrentChanged

onCurrentChanging

onPageChanged

onPageChanging

onSourceCollectionChanged

  • onSourceCollectionChanged(e?: EventArgs): void

onSourceCollectionChanging

refresh

  • refresh(): void

  • Re-creates the view using the current sort, filter, and group parameters.

    Returns void

remove

  • remove(item: Partial<T> | T): void

  • Removes the specified item from the collection.

    Parameters

    • item: Partial<T> | T

      Item to be removed from the collection.

    Returns void

removeAt

  • removeAt(index: number): void

  • Removes the item at the specified index from the collection.

    Parameters

    • index: number

      Index of the item to be removed from the collection. The index is relative to the view, not to the source collection.

    Returns void

Events

collectionChanged

collectionChanged: Event<ICollectionView<T>, NotifyCollectionChangedEventArgs<T>>

Occurs when the collection changes.

currentChanged

currentChanged: Event<ICollectionView<T>, EventArgs>

Occurs after the current item changes.

currentChanging

currentChanging: Event<ICollectionView<T>, CancelEventArgs>

Occurs before the current item changes.

pageChanged

pageChanged: Event<IPagedCollectionView, EventArgs>

Occurs after the page index changes.

pageChanging

pageChanging: Event<IPagedCollectionView, PageChangingEventArgs>

Occurs before the page index changes.

sourceCollectionChanged

sourceCollectionChanged: Event<ICollectionView<T>, EventArgs>

Occurs after the value of the sourceCollection property changes.

sourceCollectionChanging

sourceCollectionChanging: Event<ICollectionView<T>, CancelEventArgs>

Occurs before the value of the sourceCollection property changes.