Push函数似乎覆盖了Angular中的每个数组元素
Push函数似乎覆盖了Angular中的每个数组元素
提问于 2019-03-20 03:50:14
我正在尝试使用以下代码将一些会话消息推送到一个数组中：
myConversations: IConversation[] = [];
myConversationMessage: IConversationMessages = {
conversationId: 0,
messageId: 0,
messageText: ''
};
myConversationMessages: IConversationMessages[] = [];
this.conversationService.getConversations().subscribe(conversations => {
this.myConversations = conversations;
for (let i of this.myConversations) {
this.myConversationMessage.conversationId = i.conversationId;
for (let j of i.messages) {
this.myConversationMessage.messageId = j.messageId;
this.myConversationMessage.messageText = j.messageText;
this.myConversationMessages.push(this.myConversationMessage);
}
}
console.log(this.myConversationMessages);
});我从一个JSON对象中检索会话&会话中的消息。不是将每条消息都推送到myConversationMessages数组，而是在控制台中输出以下内容：
0
conversationId: 2
messageId:2
messageText: "testing"
1
conversationId: 2
messageId:2
messageText: "testing"
2
conversationId: 2
messageId:2
messageText: "testing"
3
conversationId: 2
messageId:2
messageText: "testing"因此，最终的“对话”对象将覆盖每个数组元素。
有人能告诉我为什么我的代码会这么做吗？提前谢谢你
附言。我可以上传进一步的代码，如果它将澄清我的问题。
回答 2
Stack Overflow用户
回答已采纳
发布于 2019-03-20 04:01:18
因为JavaScript对象是通过引用传递的：
myConversationMessages: IConversationMessages[] = [];
this.conversationService.getConversations().subscribe(conversations => {
this.myConversations = conversations;
for (let i of this.myConversations) {
this.myConversationMessage.conversationId = i.conversationId;
for (let j of i.messages) {
this.myConversationMessage.messageId = j.messageId;
this.myConversationMessage.messageText = j.messageText;
this.myConversationMessages.push(this.myConversationMessage); // <-= Here you are pushing a reference to the same object in every loop. In every loop you are updating the single object, and the reference in each array spot points to the same object
}
}
console.log(this.myConversationMessages);
});试试这个：
for (let i of this.myConversations) {
for (let j of i.messages) {
this.myConversationMessages.push({
conversationId: i.conversationId,
messageId: j.messageId,
messageText: j.messageText
});
}
}这将为每次迭代创建一个新对象。
Stack Overflow用户
发布于 2019-03-20 03:58:49
这是因为您将引用对象添加到数组中。在您的示例中，您没有向数组中添加3个对象，而是三次添加了一个对象的三个引用。其中一个属性的更改会导致所有其他属性的更改。
它应该是作品：
for (let i of this.myConversations) {
this.myConversationMessage.conversationId = i.conversationId;
for (let j of i.messages) {
let item = new IConversationMessages();
item.messageId = j.messageId;
item.messageText = j.messageText;
this.myConversationMessages.push(item);
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/55248989
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