错误：无法读取未定义的属性“ forEach”

Question

我想做什么：

我想过滤这些数组，看看是否有同时处于活动状态的日期。

这是我的代码：

loadAllAndCheckDates (recommendedSection: RecommendedSection): boolean {
        this.query()
            .subscribe((res: ResponseWrapper) => { this.fromDbRecommendedSections = res.json; }, (res: ResponseWrapper) => this.onError(res.json));

        return this.checkDates(recommendedSection);
    }

    checkDates (currentRecSec: RecommendedSection): boolean {

        this.fromDbRecommendedSections.forEach((recSecDB:RecommendedSection) =>{
            var dbActiveFrom = new Date(recSecDB.activeFrom);
            var dbActiveTo = new Date(recSecDB.activeTo);
            var currActiveFrom = new Date(currentRecSec.activeFrom);
            var currActiveTo = new Date(currentRecSec.activeTo);
             if(dbActiveFrom.getTime() === currActiveFrom.getTime()){
                this.isDouble = true;
             }if (dbActiveTo.getTime() === currActiveTo.getTime()){
                this.isDouble = true;
             }if(dbActiveFrom > currActiveFrom && dbActiveFrom < currActiveTo){
                 this.isDouble = true;
             }if(dbActiveTo > currActiveFrom && dbActiveTo < currActiveTo){
                 this.isDouble = true;
             }
        }, (res: ResponseWrapper) => this.onError(res.json));
        return this.isDouble;
    }

问题：

可悲的是，我在控制台中收到以下错误：无法读取未定义的属性'forEach'

编辑：

以下是设置fromDbRecommendedSection的方法：

export class RecommendedSection implements BaseEntity {
    constructor(
        public id?: number,
        public activeFrom?: any,
        public activeTo?: any,
        public identification?: string,
        public recommendedSectionNames?: RecommendedSectionName,
        public recommendedSectionItems?: RecommendedSectionItem[],
    ) {
        this.recommendedSectionItems = [];
    }
}

Answer 1

在您的示例中，您应该同步处理数据，在填充this.fromDbRecommendedSections之前，获得响应的延迟可能太高。因此，当您返回this.checkDates this.fromDbRecommendedSections时，就是undefined。

尝试

loadAllAndCheckDates (recommendedSection: RecommendedSection): boolean {
        this.query()
            .subscribe((res: ResponseWrapper) => {
                this.fromDbRecommendedSections = res.json; // needs to be an array
                this.checkDates(recommendedSection)
            }, (error:any) => console.log(error);
    }