“在声明实例方法之后,不允许声明实例字段.相反,这应该出现在类/接口的开头.(成员排序)”

我想了解如何解决这个以及为什么我得到这个.

该错误与下一个代码中的私有函数有关：

export class HomeComponent implements OnInit {
public error: string;
public shirts = [];


constructor(public rest: RestService,public scService: ShoppingCartService,public snackBar: MdSnackBar) {
}


ngOnInit() {
    this.rest.getAll().subscribe((r: any) => {
        this.shirts = r;
    },error => {
        this.error = 'Opps there\'s some error';
    });

}

addToCart(shirt: any) {
    this.scService.add(shirt);
    this.showSnackMessage('Added to Chart List');
}

showSnackMessage(message: string) {
    this.snackBar.open(message,null,{
        duration: 1000
    });
}
//Here the error is showed
private sizescore = {
    'string': -1,s: 0,m: 1,l: 2,'x-large': 3,};

sortData(sort: Sort) {
    const data = this.shirts.slice();
    if (!sort.active || sort.direction === '') {
        this.shirts = data;
        return;
    }

    this.shirts = data.sort((a,b) => {
        let isAsc = sort.direction === 'asc';
        switch (sort.active) {
            case 'colour':
                return compare(a.colour,b.colour,isAsc);
            case 'size':
                return compare(this.sizescore[a.size],this.sizescore[b.size],isAsc);
            default:
                return 0;
        }
    });
}
}