我无法弄清楚我的第一层和第二层是如何正确映射的,但是我的第三层给了我一个错误。我可以借一双新眼睛吗?我做错了什么?
以下是我的数据样本(json)
exports.LicenseItems = [
{
id: 100,
network_name: "scala",
licenseProperties: [
{ id: 101, name: "Item 1: ", value: " Value 1" },
{ id: 102, name: "Item 2 ", value: " Value 2" },
{ id: 103, name: "Item 3 ", value: " Value 3" },
{
id: 104,
name: "Item 4",
Licenses: [
{id: 1041, name: "SubItem 4.1", value: " SubValue 1"},
{id: 1042, name: "SubItem 4.2", value: " SubValue 2"},
{id: 1043, name: "SubItem 4.3", value: " SubValue 3"},
],
},
{
id: 105,
name: "Item 5",
Licenses: [
{id: 1051, name: "SubItem 5.1", value: " SubValue 1"},
{id: 1052, name: "SubItem 5.2", value: " SubValue 1"},
{id: 1053, name: "SubItem 5.3", value: " SubValue 1"},
],
},
{ id: 106, name: "Item 6", value: " Value 6" },
{ id: 107, name: "Item 7", value: " Value 7" },
{ id: 108, name: "Item 8", value: " Value 8" },
],
},
{...},
{...},
];
这是我在ReactJS中的映射脚本
{LicenseItems.map((item, index) => (
<Grid item xs={12} style={{padding: 0}} key={index}>
<ListItem
divider
button
onClick={this.handleClick}>
<ListItemText primary={<CMLabel>{item.network_name}</CMLabel>}/>
<IconButton>
<Icon>{this.state.open ? 'expand_more' : 'expand_less'}</Icon>
</IconButton>
</ListItem>
<Collapse
in={!this.state.open}
timeout="auto"
unmountOnExit
className={classes.submenu}>
<List component="div" disablePadding>
{item.licenseProperties.map((properties, propertyIndex) => (
<ListItem key={propertyIndex}>
<ListItemText
primary={
<span>
<CMLabel>{properties.name}</CMLabel> {properties.value}
<div className={classes.subdueList}>
{properties.Licenses.map((row, featuredIndex) => (
<span key={featuredIndex}>
<CMLabel>{row.name}</CMLabel> {row.value}
</span>
))}
</div>
</span>
}
/>
</ListItem>
))}
</List>
</Collapse>
</Grid>
))}
我的输出呈现第一级(LicenseItems)和第二级(licenseProperties)。但是thrid映射级别(Licenses)不会呈现并给我这个错误
未捕获(承诺)TypeError:无法读取未定义
的属性“map”
查看图片以获得一些视觉帮助
先谢谢你们!
答案 0 :(得分:1)
在您的代码中,在此行:
{properties.Licenses.map((row, featuredIndex)
在某些数据中,属性对象没有Licenses
字段,因此您收到此错误。
您可以在首先映射之前检查它是否存在,例如
<div className={classes.subdueList}>
{properties.Licenses!=null ? properties.Licenses.map((row, featuredIndex) => (
<span key={featuredIndex}>
<CMLabel>{row.name}</CMLabel> {row.value}
</span>
)):<div/>}
</div>