breezejs：非标量导航属性是只读的

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我有一个控件（KendoMulti-Select），它绑定到ParentItemType.users属性（AngularJS绑定），它允许 select 列表中的用户（使用 breeze-kendo 网桥和 'webApiOData' 适配器检索）。

选择用户会导致 setNpValue (https://github.com/Breeze/breeze.js/blob/397b2a02aa2173175c304eb1b37332f1656db6f5/src/a35_defaultPropertyInterceptor.js#L287) 中出现 "Error: Nonscalar navigation properties are readonly - entities can be added or removed but the collection may not be changed." 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

处遇到异常

context.newValue 是一个用户实体数组。

这是我的元数据定义中某处的错误吗？其实我只是想在我的 ParentItem 中有多个用户。

Breeze版本：1.5.4

Answer 1

不，这不是您的元数据定义中的错误。这是设计使然。非标量导航属性由 Breeze 管理。 Multi-select 控件尝试获取值数组的所有权并将其替换为新数组。 Breeze 不允许这样做，因为这将是灾难性的，会破坏您的实体。

Multi-select 控件有点麻烦。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根据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 的示例，但是 FWIW，这是 DevExpress TagBox 和以下实体模型的 Angular2 示例。

模型（主题）1<--->n SubjectVehicleAssociation n<--->1 LookupItem（车辆）

涉及一些工作。开箱即用的 multi-select 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>

在组件中创建适配器实例：

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);

以及适配器实现：

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：非标量导航属性是只读的

breezejs: Nonscalar navigation properties are readonly

kendo-ui

angularjs

breeze