我正在开发一个应用，使用Ionic Angular和PHP作为后端.我正在从PHP返回这个JSON字符串，我正在接收它，

我正在开发一个使用Ionic Angular和PHP作为后端的应用程序。我从PHP返回这个JSON字符串我接收到的是Angular中的

[
{
    "HistoryId":"440",
    "TotalPrice":"24",
    "aa":[{"orderid":"630","foodId":"1","quantity":"1","name":"Mixed Starter (Minimum For Two)","price":"9"},         {"orderid":"641","foodId":"3","quantity":"1","name":"Sesame chicken on toast","price":"5"},
          {"orderid":"662","foodId":"2","quantity":"2","name":"Sesame prawn on toast","price":"5"}]
},
{
    "HistoryId":"451",
    "TotalPrice":"24",
    "aa":[{"orderid":"650","foodId":"1","quantity":"1","name":"Mixed Starter (Minimum For Two) ","price":"9"},        {"orderid":"671","foodId":"3","quantity":"1","name":"Sesame chicken on toast","price":"5"},
          {"orderid":"682","foodId":"2","quantity":"2","name":"Sesame prawn on toast","price":"5"}]
}
]

但是当我试着展示它的时候我收到这个错误:

Error: [ngRepeat:dupes] Duplicates in
a repeater are not allowed. Use 'track by' expression 
to specify unique keys. Repeater: oh in orderHistory,
Duplicate key: string:", Duplicate value: "