Question

我有两个TypeScript类：

export class AbsenceWithUser {
    @jsonProperty(Absence) public readonly absence: Absence;
    @jsonProperty(User) public readonly user: User;

    constructor(absence: Absence, user: User) {
        this.absence = absence;
        this.user = user;
    }
}

export class Birthday {
    @jsonProperty(MomentDateJson) public readonly birthday: moment.Moment;
    @jsonProperty(User) public readonly user: User;

    constructor(birthday: moment.Moment, user: User) {
        this.birthday = birthday;
        this.user = user;
    }
}

我需要创建一个数组，其中的元素可以是AbsenceWithUser或Birthday的实例。我使用以下方法执行此操作：

private getAllEvents():(AbsenceWithUser|Birthday)[] {
    const absences = this.props.absences as (AbsenceWithUser|Birthday)[];
    const birthdays = this.props.birthdays as (AbsenceWithUser|Birthday)[];
    return absences.concat(birthdays);
}

但是，如果我使用getAllEvents创建数组，则其元素不会被识别为任何一个类的实例。我有以下功能：

private eventToDate(x:AbsenceWithUser | Birthday):Moment {
    if (x instanceof AbsenceWithUser) {
        return x.absence.endDate;
    } else if (x instanceof Birthday) {
        return x.birthday;
    } else {
        throw new Error("Unknown event type, x: " + x);
    }
}

以下代码会生成错误＆＃34;未知事件类型＆＃34;。

const events = this.getAllEvents();
this.eventToDate(events[0]);

我应该如何更改代码，以便区分AbsenceWithUser中的Birthday和eventToDate？

请注意，它不需要instanceof。

更新1（2017年10月1日13:27 MSK）：

尝试将getEvents方法更改为：

private getAllEvents():(AbsenceWithUser|Birthday)[] {
    const absences:(AbsenceWithUser|Birthday) = this.props.absences as (AbsenceWithUser|Birthday)[];
    const birthdays:(AbsenceWithUser|Birthday) = this.props.birthdays as (AbsenceWithUser|Birthday)[];
    return absences.concat(birthdays);
}

现在我在WebStorm中收到Error:(127, 15) TS2322:Type '(AbsenceWithUser | Birthday)[]' is not assignable to type 'AbsenceWithUser | Birthday'. Type '(AbsenceWithUser | Birthday)[]' is not assignable to type 'Birthday'. Property 'birthday' is missing in type '(AbsenceWithUser | Birthday)[]'.等错误。

更新2（13:31 01.10.2017 MSK）：我尝试创建一个空数组，然后使用concat将缺席和生日数组合并为一个。为此我创建了以下数组：

const a:(AbsenceWithUser|Birthday) = [];

WebStorm报告此错误：Error:(127, 15) TS2322:Type 'never[]' is not assignable to type 'AbsenceWithUser | Birthday'. Type 'never[]' is not assignable to type 'Birthday'. Property 'birthday' is missing in type 'never[]'.

我不知道never[]类型来自何处。

更新3（13:46 01.10.2017 MSK）：修复了getAllEvents中明显的类型错误。

private getAllEvents():(AbsenceWithUser|Birthday)[] {
    const absences:(AbsenceWithUser|Birthday)[] = this.props.absences as (AbsenceWithUser|Birthday)[];
    const birthdays:(AbsenceWithUser|Birthday)[] = this.props.birthdays as (AbsenceWithUser|Birthday)[];
    const allEvents:(AbsenceWithUser|Birthday)[] = absences.concat(birthdays);
    return allEvents;
}

更新4（14:01 01.10.2017 MSK）：

另一次尝试：

export type EventTypes = (AbsenceWithUser|Birthday);

private isEmpty(arr:EventTypes[]):boolean {
    return arr.length === 0;
}

private getAllEvents():EventTypes[] {
    const absences:EventTypes[] = this.props.absences as EventTypes[];
    const birthdays:EventTypes[] = this.props.birthdays as EventTypes[];
    const absencesEmpty:boolean = this.isEmpty(absences);
    const birthdaysEmpty:boolean = this.isEmpty(birthdays)
    if (absencesEmpty && !birthdaysEmpty) {
        return birthdays;
    } else if (absencesEmpty && birthdaysEmpty) {
        return [];
    } else if (!absencesEmpty && !birthdaysEmpty) {
        return absences.concat(birthdays);
    } else if (!absencesEmpty && birthdaysEmpty) {
        return absences;
    }
    return [];
}

更新5（20:08 01.10.2017 MSK）：最终版本：

private getAllEvents():EventTypes[] {
    const absences:EventTypes[] = this.props.absences.map(absenceJson => {
        return new AbsenceWithUser(absenceJson.absence, absenceJson.user);
    });
    const birthdays:EventTypes[] = this.props.birthdays.map(birthdayJson => {
        return new Birthday(birthdayJson.birthday, birthdayJson.user);
    });
    const absencesEmpty = this.isEmpty(absences);
    const birthdaysEmpty = this.isEmpty(birthdays);
    if (absencesEmpty && birthdaysEmpty) {
        return [];
    } else if (absencesEmpty && !birthdaysEmpty) {
        return birthdays;
    } else if (!absencesEmpty && birthdaysEmpty) {
        return absences;
    } else {
        return absences.concat(birthdays);
    }
}

请注意，理论上您可以使用Object.assign将从JSON反序列化的对象转换为Typescript类实例（如果您的环境支持它）。

Answer 1

我创建了一个示例，演示如何将特定类型的两个数组合并到一个可以包含两种类型项的数组中。您可以使用instanceof检查类型。

class AbsenceWithUser {
    public readonly when: string;
    public readonly user: string;
}

class Birthday {
    public readonly day: string;
    public readonly user: string;
}

class Test {

    constructor(){
      let absences : AbsenceWithUser[] = [new AbsenceWithUser(), new AbsenceWithUser()]
      let birthdays : Birthday[] = [new Birthday(), new Birthday(), new Birthday()]

      let combined:(AbsenceWithUser | Birthday)[] = this.mergeArrays(absences, birthdays)

      if (combined[0] instanceof Birthday) {
        console.log("we have a birthday")
      } else { 
        console.log("we have an absence")
      }

    }

    private mergeArrays(absences: AbsenceWithUser[], birthdays: Birthday[]): (AbsenceWithUser | Birthday)[] {
        var allEvents : (AbsenceWithUser | Birthday)[] = [...birthdays].concat(...absences);
        return allEvents;
    }
}

为什么我会得到＃34;错误的类型＆＃34;错误在这里？

1 个答案: