想象一下按下按钮就可以点赞的帖子。此按钮会修改远程数据库,因此将喜欢的内容关联到特定帖子需要一些时间。
现在,如果用户使用以下代码开始如此快速地按下按钮:
state = {
isLiked: false,
}
handlePress = () => {
this.setState(
{
isLiked: !this.state.isLiked,
},
this.handleLike
);
};
handleLike = async () => {
const { postId } = this.props;
try {
console.log(isLiked ? "Liking" : "Disliking")
await db.processLike(postId);
} catch (err) {
// If an error has occurred, reverse the 'isLiked' state
this.setState({
isLiked: !this.state.isLiked,
});
// TODO - Alert the error to the user in a toast
console.log(err);
}
console.log("DONE");
};
由于一切都是异步的,因此可以看到这种情况:
喜欢
不喜欢
完成<---------- 不喜欢完成
完成<---------- 喜欢完成
我想创建一个状态“isLiking”以避免在所有异步作业完成之前运行代码。像这样的东西:
state = {
isLiking: false,
isLiked: false,
}
handlePress = () => {
if (this.state.isLiking) return; <------------------------------------
this.setState(
{
isLiking: true, <------------------------------------
isLiked: !this.state.isLiked,
},
this.handleLike
);
};
handleLike = async () => {
const { postId } = this.props;
try {
console.log(isLiked ? "Liking" : "Disliking");
await db.processLike(postId);
} catch (err) {
// If an error has occurred, reverse the 'isLiked' state
this.setState({
isLiked: !this.state.isLiked,
});
// TODO - Alert the error to the user in a toast
console.log(err);
}
this.setState({ isLiking: false }); <------------------------------------
console.log("DONE");
};
一切顺利,但如果用户快速按下按钮,在代码中描述的所有过程之前,他将无法看到 GUI 更改(喜欢按钮颜色(红色表示喜欢,白色表示不喜欢))以上完成。
我还想过像这样制作一个去抖动函数(对于handlePress):
export const debounce = (func, wait, immediate) => {
/*
Returns a function, that, as long as it continues to be invoked, will not
be triggered. The function will be called after it stops being called for
N milliseconds. If `immediate` is passed, trigger the function on the
leading edge, instead of the trailing.
*/
let timeout;
return function () {
let context = this,
args = arguments;
let later = function () {
timeout = null;
if (!immediate) func.apply(context, args);
};
let callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow) func.apply(context, args);
};
};
...
debuncedHandlePress = debounce(this.handlePress, 500); // Now, when the button is pressed, it will call this function, instead of the original handlePress
但是有了这个,我唯一要做的就是减少获得混乱结果的机会。也就是说,我仍然遇到与第一个代码相同的问题。
任何想法以这样的方式做我想做的事情,即我得到的结果是有序的并避免等待写入数据库的时间?
谢谢你。