问题描述
尝试将DocumentID与列表中Firestore DocumentReference对象的ID进行比较。并遇到了这种奇怪的行为。我想从列表中获取正确的对象。我在做什么错了？
DocumentReference _resolveReferenceFromID(
List<DocumentReference> references,String documentID) {
references.forEach((element) {
print('element id: ${element.documentID}');
print('document id: $documentID');
if (element.documentID == documentID) {
return element;
}
});
print('something is wrong here');
return null;
}
这是输出：
element id: W24buSwq7cYOahJz6Gdq
document id: W24buSwq7cYOahJz6Gdq
element id: cBOIXvebYYIpox5cAcct
document id: W24buSwq7cYOahJz6Gdq
something is wrong here
Flutter --version：
Flutter 1.22.0-2.0.pre.36 • channel master • https://github.com/Flutter/Flutter.git
Framework • revision d30e36ba8c (6 days ago) • 2020-08-21 22:36:03 -0400
Engine • revision d495da20d0
Tools • Dart 2.10.0 (build 2.10.0-49.0.dev)
颤抖的医生：
Doctor summary (to see all details,run Flutter doctor -v):
[√] Flutter (Channel master,1.22.0-2.0.pre.36,on Microsoft Windows [Version 10.0.18362.1016],locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
[√] Chrome - develop for the web
[√] Android Studio (version 4.0)
[√] VS Code (version 1.48.2)
[√] Connected device (3 available)
• No issues found!
解决方法
您正在使用<style>遍历元素。 forEach函数参数内的return element仅从该函数返回，而不从周围的forEach函数返回。
将其更改为：
_resolveReferenceFromID然后DocumentReference _resolveReferenceFromID(
List<DocumentReference> references,String documentID) {
for (var element in references) {
print('element id: ${element.documentID}');
print('document id: $documentID');
if (element.documentID == documentID) {
return element;
}
}
print('something is wrong here');
return null;
}
从所需的函数返回。