Error TS6138 - Property xxxx is declared but its value is never read

我有一段 TypeScript 代码：

export class AppModule {
  constructor(private s: ActiveCartService){
    if( s === undefined){
      console.log(s);
    }
    s.isStable().subscribe((data) => console.log('isStable: ' , data));
  }
}

引起如下错误消息：

Error TS6138 - Property xxxx is declared but its value is never read

解决方法：

修改 ​​tsconfig.json​​:

将下列参数改成 false 即可：

"noUnusedLocals": false,
 "noUnusedParameters": false,

问题解决：