英文:
Filter ids from an object list
问题
我需要从对象列表中筛选出ID，并将这些ID存储在一个新数组中。请建议一种方法来完成这个任务。根据以下示例，我需要从“_studentDetails”列表中筛选出ID，并将这些ID存储在“_idList”数组中。
示例：
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id: 1, name: 'Peter', age: 14),
Student(id: 2, name: 'Anne', age: 20),
];
英文:
I need to filter ids from an object list and add those id list to a new array.Please suggest a way to do this.As per the below example I need to filter the ids from the '_studentDetails' list and store those ids in '_idList' array.
Example:
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id:1 , name:'Peter' , age: 14),
Student(id:2 , name:'Anne' , age: 20),
];
答案1
得分: 1
你可以使用 list.map() 方法来实现这个，遍历列表项，对于每个项，返回其属性 id 的值，然后将所有返回的值转换为列表：
List<int> _idList = _studentDetails.map((student) => student.id).toList();
英文:
You can achieve this using list.map() method<br>
you loop through the list items and for every one you return the value of its preoperty id then convert all the returned values to list:
List<int> _idList = _studentDetails.map((student) => student.id).toList();
答案2
得分: 0
如果你只想要ID列表，你可以使用.map方法：
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id:1 , name:'Peter' , age: 14),
Student(id:2 , name:'Anne' , age: 20),
];
_idList.addAll(
_studentDetails.map((student) => student.id),
);
英文:
If you just want the list of ids, you can use the method .map:
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id:1 , name:'Peter' , age: 14),
Student(id:2 , name:'Anne' , age: 20),
];
_idList.addAll(
_studentDetails.map((student) => student.id),
);
答案3
得分: 0
你还可以使用 forEach() 循环 来实现这一点。
下面是代码：
void main(){
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id: 1, name: 'Peter', age: 14),
Student(id: 2, name: 'Anne', age: 20),
];
_studentDetails.forEach((element) {
_idList.add(element.id);
});
print(_idList);
}
class Student{
int id;
String? name;
int? age;
Student({required this.id, required this.name, required this age});
}
英文:
You can also achieve this using forEach() loop
Below the code:
void main(){
List<int> _idList = [];
List<Student> _studentDetails = [];
_studentDetails = [
Student(id:1 , name:'Peter' , age: 14),
Student(id:2 , name:'Anne' , age: 20),
];
_studentDetails.forEach((element) {
_idList.add(element.id);
} );
print(_idList);
}
class Student{
int id;
String? name;
int? age;
Student({required this.id, required this.name, required this.age});
}
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