仅HTML中显示的第一个元素

我正在组件的NgOnInit函数中加载一个“Client”数组。在这个调用之后,我想初始化一个类型为“TimeSheet”的数组,它将“Client”作为元素。我是这样做的:

init(clients : Client[]) {
    let i = 0;
    this.timeSheets = new Array(clients.length);
    for(let client of clients) {
        console.log("client firstname" + client.firstName);
        this.timeSheets[i] = new TimeSheet();
        this.timeSheets[i].client = client;
        console.log("client last name in timesheet: " + 
        this.timeSheets[i].client.lastName);
        i++;
    }
}    

浏览器控制台显示客户端的正确值:

client firstname Hans
client last name in timesheet: Müller
client firstname John
client last name in timesheet: Smith
client firstname Marie
client last name in timesheet: Curie

但是,在我的HTML模板中,只显示第一个元素。这是我放在前端的部分:

<tr *ngFor="let timeSheet of timeSheets ;trackBy: trackId">
    <td>{{timeSheet.client.lastName}}</td>
    <td>{{timesheet.client.firstName}}</td>
    <td><input type="text" (change)="calculate($index)"></td>
    <td><input type="text"></td>
</tr>

ERROR TypeError: Cannot read property 'client' of undefined

它看起来是这样的:

另外,按钮标签和表头也不见了,所以我推测代码中有一些错误。请帮我找到它。