小编Ste*_*eve的帖子

我有一个 postgresql 表并尝试将美国境内的随机地理位置插入到列中geo_location。然而，我的纬度/经度有点偏差，有些点显示在海洋中。因此，我去获取美国的精确多边形，并且需要这些点仅在位于该多边形内时才显示。有谁知道如何做到这一点？

INSERT INTO test_dataset
(first_name, last_name, geo_location)
select 
       substr(md5(random()::text), 1, 7),
       substr(md5(random()::text), 1, 10),
       (random() * (47.606209 - 25.427152)) + 25.427152 || ',' || (random() * (-124.389641 - -69.082237)) + -69.082237
FROM generate_series(1, 20);  

 

美国多边形

  POLYGON((-125.016047790785 48.208785494735764,-124.14089035719684 40.86877099667271,-121.5599275789894 36.06717734117032,-117.28671864846486 32.64978455562844,-113.72654637400285 32.31983439152819,-108.30080609779633 31.38368862238211,-105.8560247727104 31.460910518060302,-103.3967999601722 28.907930814307832,-101.79828909376985 29.931584620558965,-99.88202150341736 28.5312922037797,-97.23709470934983 25.954713168125338,-97.10002896107818 28.035767664456188,-94.14206168386124 29.48328979323645,-89.95286079259995 29.22199958232973,-88.80769857316915 30.441930703667964,-85.20950160725116 30.01610257057618,-83.55763826679038 29.988533620710356,-81.11550982715487 25.210558232017902,-79.82296508270082 26.439779557216667,-81.15323975356083 30.633102305542167,-80.61057729642516 32.67360737502075,-76.42226070031401 35.08303539533796,-76.74443890001484 38.7701053822278,-75.94326749398839 39.537424403566234,-75.85778562947489 37.61762713466268,-73.584262798466 41.05930212093591,-70.25489155819044 41.81899403776205,-70.84147400778302 43.17550270250865,-66.71653189743186 44.621194501738415,-67.98343208253185 47.27220127731093,-69.31075910289138 47.37130972398248,-70.71885174696367 45.18697869058366,-75.17835218911763 44.78963172176475,-77.22343210634047 43.57594231004268,-78.78804499198748 43.38258742737503,-82.22588977068015 41.561458542619334,-83.6165912767997 41.73128368552776,-83.54290001428807 45.0297037216441,-85.31768038061823 45.46571539393534,-86.68244256233366 41.733923340223015,-87.68199084704145 …

我有一个基本的 Material UI v4 数据网格。我正在尝试将 16 的任何行更改age为全灰色color: 'grey'。我正在努力做到这一点。该文档对于如何更改整行字体颜色不是很清楚。这是代码。

import * as React from "react";
import { DataGrid } from "@material-ui/data-grid";

const columns = [
  { field: "id", headerName: "ID", width: 70 },
  { field: "firstName", headerName: "First name", width: 130 },
  { field: "lastName", headerName: "Last name", width: 130 },
  {
    field: "age",
    headerName: "Age",
    type: "number",
    width: 90
  },
  {
    field: "fullName",
    headerName: "Full name",
    description: "This column has a value getter and is not …

我在反应中映射一个对象数组。数组如下

const tabs = [
    {
        index: 0,
        title: 'v1',
        path: '/v1',
        component: versionManager,
    },
    {
        index: 1,
        title: 'v2',
        path: '/v2',
        component: version2Manager,
    },
    {
        index: 0,
        title: 'v3',
        path: '/v3',
        component: version3Manager,
    },
];

我已经成功地用这个映射了整个数组

{tabs.map((item) => {
           if (auth.verify(Roles.role1)) {
                   return (
                        <Tab
                             label={item.title}
                             key={item.index}
                             component={Link}
                             to={item.path}
                         />
                    );

但我想添加一个 else 只映射第一个对象（v1）及其所有元素，类似于此。

} else {
       return (
             <Tab
                 label={item.title}
                 key={item.index}
                 component={Link}
                 to={item.path}
              />
                )
 }

我尝试过诸如 item.title[0]、item.index[0] 等之类的东西......但它每次都会给出一个未定义的错误。有谁知道在 else 语句中只映射第一个对象的最佳方法？提前致谢。

我已经在 React 中看到从对象数组中获取第一个对象，但这对我来说似乎没有帮助。