打字稿-无法分配给打字生

Question

我在构造函数中有错误>> this.allStudents

class Students {
    public StudentsId: number;
    public StudentsName: string;
    public allStudents?: Students[];
    constructor() {
        this.allStudents = [
            { StudentsId: 100, StudentsName: 'Mahmoud'},
            { StudentsId: 101, StudentsName: 'Sami' },
            { StudentsId: 102, StudentsName: 'Osama' },
            { StudentsId: 103, StudentsName: 'Amer' },
            { StudentsId: 104, StudentsName: 'Ahmad' },
            { StudentsId: 105, StudentsName: 'Fadi' }
        ];
    }

    get getAllStudents() {
        return null;
    }
    getStudentById(_studentsId) {
        return this.allStudents.filter(x => x.StudentsId === _studentsId);
    }
    set addStudent(_student) {

    }


}

我不知道为什么会发生此错误。我需要一些帮助来解决此问题。

如何在类students中使用此接口？请检查界面IStudents，如下所示：

interface IStudents {
    name: string,
    age: number,
    active:boolean
};

Answer 1

我看不到为什么需要Students的递归结构，所以用您感兴趣的属性定义Student并引用它。可以是类，接口或类型。

下面的示例将Student与Students的列表分开，您可能需要更改名称以使其更明确。

interface Student {
    StudentsId: number;
    StudentsName: string;
}

class Students {
    public StudentsId: number;
    public StudentsName: string;
    public allStudents: Student[] = [];

    constructor() {
        this.allStudents = [
            { StudentsId: 100, StudentsName: 'Mahmoud'},
            { StudentsId: 101, StudentsName: 'Sami' },
            { StudentsId: 102, StudentsName: 'Osama' },
            { StudentsId: 103, StudentsName: 'Amer' },
            { StudentsId: 104, StudentsName: 'Ahmad' },
            { StudentsId: 105, StudentsName: 'Fadi' }
        ];
    }

    get getAllStudents() {
        return null;
    }

    getStudentById(_studentsId) {
        return this.allStudents.filter(x => x.StudentsId === _studentsId);
    }

    set addStudent(_student) {

    }
}

学生等级

如果您确实需要学生的等级制度，则可以这样实现：

class Students {
    public subStudents: Students[] = [];

    constructor(public StudentsId: number, public StudentsName: string) {
        this.subStudents = [
            new Students(100, 'Mahmoud'),
            new Students(101, 'Sami'),
            new Students(102, 'Osama'),
            new Students(103, 'Amer'),
            new Students(104, 'Ahmad'),
            new Students(105, 'Fadi'),
        ];
    }

    get getAllStudents() {
        return null;
    }
    getStudentById(_studentsId) {
        return this.subStudents.filter(x => x.StudentsId === _studentsId);
    }
    set addStudent(_student) {

    }
}

数组类型的可选性

我在两个代码示例中都表达了我的观点，即不希望使用null数组。您可以将其设为非可选并将其实例化为空数组，从而无需在使用前对数组进行空检查。