我有一个国家清单,我想显示一些与该国家有关的信息。我运行一个循环以显示每个国家的信息。我已经为一个国家创建了一个组件。
const CountryCard = ({ info }) => {
const { country, infoForLastDate, path } = info
return (
<Card >
<CardContent>
<Typography variant="h5" component="h2" >
{country.name}
</Typography>
<Flag oneToOne={country.oneToOne} fourToThree={country.fourToThree} />
<Typography variant="body2" >
Confirmed: {infoForLastDate.confirmed}
</Typography>
<Typography variant="body2" component="p">
Recovered: {infoForLastDate.recovered}
</Typography>
<Typography variant="body2" component="p">
Deaths: {infoForLastDate.deaths}
</Typography>
</CardContent>
<CardActions>
<Link href={path}>
See more
</Link>
</CardActions>
</Card>
)
}
export default CountryCard
此外,我还创建了另一个组件来显示与该国家/地区有关的国旗。
import React from 'react'
import { imageUrlFor } from '../lib/image-url'
const Flag = ({ oneToOne, fourToThree }) => {
const url = imageUrlFor(oneToOne.asset._id)
return (
<img src={url} />
)
}
export default Flag
我收到错误TypeError: oneToOne is null
我不知道为什么旗标会渲染两次。当我调试时,第一次oneToOne
属性具有一个值,但最后再次运行,并且是null
为什么会发生?
编辑:添加CountryList组件:
const CountryList = ({list}) => {
return (
<Grid container spacing={3}>
{ list.length > 1 && list.map(country => {
const countryWithPath = {
...country,
path: `/country/${country.country.name.toLowerCase().replace(' ', '-').replace('*', '')}`
}
return (
<Grid item xs={12} sm={6} key={country._id} >
<CountryCard info={countryWithPath} />
</Grid>)
})
}
</Grid>
)
}
export default CountryList