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error in distinctUntilChaned if no comparer function provided(如果未提供比较器函数,则DisttUntilChaned出错)

转载 作者:bug小助手 更新时间:2023-10-25 18:18:53 25 4
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given this code:

给定此代码:


/**
* Create a stream from an array of car objects.
*/
from([
{ name: 'Porsche', model: '911' },
{ name: 'Porsche', model: '911' },
{ name: 'Ferrari', model: 'F40' }
]).pipe(
/**
* Use keySelectorFn to return car names for use in comparison
*/
distinctUntilChanged(null, (car) => car.name)
)
.subscribe(console.log);

// console output:
// {name: "Porsche", model: "911"}
// {name: "Ferrari", model: "F40"}

TS complains that Argument of type 'null' is not assignable to parameter of type '(previous: unknown, current: unknown) => boolean'.

TS报告类型为‘Null’的参数不能赋值给类型为‘(Previor:Uncern,Current:Uncern)=>Boolean’的参数。


If I change it to undefined, the same error.

如果我将其更改为未定义,则会出现相同的错误。


Even in the rxjs docs is undefined used:

即使在rxjs文档中也未定义使用:


// A stream of updates to a given account
const accountUpdates$ = of(
{ updatedBy: 'blesh', data: [] },
{ updatedBy: 'blesh', data: [] },
{ updatedBy: 'ncjamieson', data: [] },
{ updatedBy: 'ncjamieson', data: [] },
{ updatedBy: 'blesh', data: [] }
);

// We only want the events where it changed hands
const changedHands$ = accountUpdates$.pipe(
distinctUntilChanged(undefined, update => update.updatedBy)
);

In this code example I also get the same error.

在此代码示例中,我也收到了相同的错误。


So, the question is: how to set the comparer function to null/undefined without error?

因此,问题是:如何将比较器函数设置为空/未定义而不出错?


My TS version is 4.9.3. RxJs version is 7.5.0.

我的TS版本是4.9.3。RxJs版本为7.5.0。


更多回答

I have added it to the question at the end.

我已经把它加到了问题的末尾。

优秀答案推荐

This looks like it may be a quirk in the typing for distinctUntilChanged. The error would probably go away if you disabled strictNullChecks in your tsconfig.json file.

这看起来可能是differtUntilChanged的输入过程中的一个怪癖。如果您在tsfig.json文件中禁用了strictNullChecks,该错误可能会消失。


However, you can just use distinctUntilKeyChanged instead:

但是,您可以只使用DistertUntilKeyChanged:


distinctUntilKeyChanged('name');


distinctUntilChanged((prev:any,curr:any) => prev.name === curr.name)

更多回答

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