Question

我有以下元数据：

var entityTypeParent = {
    shortName: 'ParentItemType',
    namespace: 'MyNamespace',
    autoGeneratedKeyType: Identity,
    defaultResourceName: 'ParentItemTypes',

    dataProperties: {
        id: { dataType: DT.Int32, isPartOfKey: true }
    },

    navigationProperties: {
        users: {
            entityTypeName: 'User',
            isScalar: false,
            associationName: 'ParentItem_User'
        }
    }
};

var entityTypeUser = {
    shortName: 'User',
    namespace: 'MyNamespace',
    autoGeneratedKeyType: Identity,
    defaultResourceName: 'Users',

    dataProperties: {
        loginName: { dataType: DT.String, isPartOfKey: true },
        displayText: {},
        parentItemId: {
            dataType: DT.Int32
        }
    },

    navigationProperties: {
        agendaTask: {
            entityTypeName: 'ParentItemType',
            associationName: 'ParentItem_User',
            foreignKeyNames: ['parentItemId']
        }
    }
};

在UI中我有一个控件（Kendo Multi-Select），它绑定到ParentItemType.users属性（AngularJS绑定），允许从列表中选择一个用户（使用breeze-kendo bridge和'webApiOData检索） '适配器）。

选择用户会导致“错误：非标量导航属性是只读的 - 可以添加或删除实体，但可能不会更改集合。” setNpValue（https://github.com/Breeze/breeze.js/blob/397b2a02aa2173175c304eb1b37332f1656db6f5/src/a35_defaultPropertyInterceptor.js#L287）中的异常。

如果我将定义更改为isScalar eq true。我在https://github.com/Breeze/breeze.js/blob/397b2a02aa2173175c304eb1b37332f1656db6f5/src/a35_defaultPropertyInterceptor.js#L298

处获得了例外

context.newValue是一个用户实体数组。

这是我的元数据定义中的某个错误吗？实际上我只想在ParentItem中拥有多个用户。

Breeze版本：1.5.4

Answer 1

不，这不是元数据定义中的错误。这是设计的。非标量导航属性由Breeze管理。多选控件尝试获取值数组的所有权并将其替换为新数组。微风不会允许这样做，因为这将是灾难性的并打破你的实体。

多选控制有点痛苦。您需要利用控件触发的事件在用户进行选择时更新导航属性，并从所选值手动创建关联实体，并在用户取消选择时删除它们。我没有KendoUI的例子，但是FWIW，这里是DevExpress TagBox和以下实体模型的Angular2示例。

模型（主题）1＆lt; ---＆gt; n SubjectVehicleAssociation n＆lt; ---＆gt; 1 LookupItem（Vehicle）

涉及到一些工作。开箱即用的多选控件仅适用于基本数组。

<dx-tag-box [dataSource]="adapter.dataSource"
        displayExpr="description"
        [value]="adapter.value"
        [searchEnabled]="true"
        (onSelectionChanged)="adapter.selectionChanged($event)">

</dx-tag-box>

组件中的适配器实例创建：

let valueConverter: ITagBoxValueConverter<SubjectVehicleAssociation, { code: string, longValue: string }> = {
    match: (item: SubjectVehicleAssociation, lookupItem: { code: string, longValue: string }) => item.abbreviation === lookupItem.code,
    seed: (item: SubjectVehicleAssociation, lookupItem: { code: string, longValue: string }) => {
        item.description = lookupItem.longValue;
        item.abbreviation = lookupItem.code;
        return item;
    }
};
this.adapter = new TagBoxAdapter(SubjectVehicleAssociation,
    () => Promise.resolve(this.vehicleAssociationsLookup),
    this.modelSubjectVehicleRelation,
    'associations',
    valueConverter);

适配器实现：

import DataSource from 'devextreme/data/data_source';
import * as _ from 'lodash';

import { Entity, EntityState } from 'breeze-client';

export interface ITagBoxValueConverter<T extends Entity, W> {

    match(value1: T, value2: W): boolean;

    seed(target: T, source: W): T;
}

export class TagBoxAdapter<T extends Entity, W> {

    dataSource: DataSource;

    constructor(private itemType: { new (): T },
        private data: (searchValue?: string, maxSearchResults?: number) => Promise<W[]>,
        private model: any,
        private valueExpr: string,
        private valueConverter: ITagBoxValueConverter<T, W>,
        private maxSearchResults: number = 20) {

        this.initializeDataSource();
    }

    get value(): T[] {
        return _.get<T[]>(this.model, this.valueExpr, []);
    }

    selectionChanged(e: { addedItems: T[], removedItems: T[] }) {

        e.addedItems.forEach(item => {
            if (item.entityAspect && item.entityAspect.entityState.isDeleted()) {
                // Real entity, needs to be resurrected
                item.entityAspect.rejectChanges();
            } else {
                // Placeholder entity, needs to be attached first
                this.model.entityAspect.entityManager.attachEntity(item, EntityState.Added);
                this.value.push(item);
            }
        })

        e.removedItems.forEach(item => {
            item.entityAspect.setDeleted();
        })

    };

    private initializeDataSource() {
        let sourceData = (searchValue: string, maxSearchResults: number) => {
            return this.data(searchValue, maxSearchResults).then((results) => {
                return results.map(dataItem => {
                    // Find existing association entity if exists
                    let item = _.find(this.value, item => this.valueConverter.match(item, dataItem));
                    if (item) return item;

                    // Not associated yet, return placeholder association entity
                    return this.valueConverter.seed(new this.itemType(), dataItem);
                })
            });
        };

        this.dataSource = new DataSource({
            // The LoadOptions interface is defined wrong it's lacking the search properties
            load: (loadOptions: any) => {
                let searchValue = loadOptions.searchValue ? loadOptions.searchValue : "";
                return sourceData(searchValue, this.maxSearchResults).then(data => data.filter(item => !_.intersection(this.value, [item]).length));
            },
            byKey: (key) => {
                return sourceData(key, 1).then((data) => _.find(data, key));
            }
        });
    }
}

breezejs：非标量导航属性只读

1 个答案: