Flutter 请求数据库

Question

我正在开发 Flutter 应用程序。我们有一个 PSQL 数据库，后台有 Node 服务器。在 Flutter 应用程序上，我显示了一些我成功从数据库中获取的几何图形。现在，在对几何图形（例如线条）进行修改后，我希望能够通过放置请求更新数据库。

服务器是这样的：

app.put('/api/shape/:id', async (req,res) =>{

    let answer;

    if( req.body.shape_type == "line"){
        answer = await db.db.modify_line(req.params.id, req.body.info_shape);
    }

    res.send(answer);
});

而 db.js 文件如下：

modify_line : async function(id_shape, info_shape){
    console.log(info_shape);
    const result = await send_query("UPDATE line SET line =  WHERE id_shape = ", [id_shape, info_shape]);
    return(result);

},

在 Flutter 应用程序上，我这样做：

_makeUpdateRequest() async {
var url = globals.URL + 'api/shape/' + globals.selectedShapeID.toString();

Map data;
if (globals.selectedType == globals.Type.line) {
  String lseg = "(" + globals.pLines[globals.selectedLineIndex].p1.dx.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p1.dy.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p2.dx.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p2.dy.toString() + ")";
  data = {
    'shape_type': 'line',
    'info_shape': {
      'id_shape': globals.selectedShapeID.toString(),
      'line': lseg,
    }
  };

} 
http.Response response;
try {
  //encode Map to JSON
  print("encode Map to JSON");
  var body = json.encode(data);
  print(body);
  response = 
  await http.put(url,
    headers: {
      "Content-Type": "application/json"
    },
    body: body
  ).catchError((error) => print(error.toString()));

} catch (e) {
  print(e);
}
return response;
}

数据库 "line" table 每行包含 "shapeID" 和 "lseg" 信息。

目前我在尝试此代码时遇到错误：

{ id_shape: '619',
  line:    '(19.5,100.6,20.5,50.9)' } 
fail____error: invalid input syntax for type lseg: "{"id_shape":"619","line":"(-19.5,100.6,20.5,50.9)"}"

我该如何塑造我的 lseg json？谢谢

Answer 1

好吧，在我看来你正在将整个 input_shape 对象传递给 SQL 查询，根据你的 console.log:

{
  id_shape: '619',
  line: '(19.5,100.6,20.5,50.9)'
}

显然，这对 Postgre 无效SQL。

我会说你的后端代码应该更像这样：

modify_line : async function(id_shape, info_shape){
    console.log(info_shape);
    const result = await send_query(
        "UPDATE line SET line =  WHERE id_shape = ",
        // Reference "line" sub-object
        [id_shape, info_shape.line],
    );
    return(result);
},

您还应注意行的 Geometric types 格式：

[ ( x1 , y1 ) , ( x2 , y2 ) ]

( ( x1 , y1 ) , ( x2 , y2 ) )

( x1 , y1 ) , ( x2 , y2 )

x1 , y1 , x2 , y2

阅读本文后我不能 100% 确定您的格式（带前导和尾随括号）是正确的。

Answer 2

问题已解决，现回复如下： DB.js 就像：

    modify_line : async function(id_shape, info_shape){
    const result = await send_query("UPDATE line SET line =  WHERE id_shape = ", [info_shape['id_shape'], info_shape['line']]);
    return(result);

},

Flutter 应用就像：

_makeUpdateRequest() async {
var url = globals.URL + 'api/shape/' + globals.selectedShapeID.toString();

Map data;
if (globals.selectedType == globals.Type.line) {
  String lseg = 
    "[" + globals.pLines[globals.selectedLineIndex].p1.dx.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p1.dy.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p2.dx.toString() + "," +
    globals.pLines[globals.selectedLineIndex].p2.dy.toString() + "]";

  data = {
    'shape_type': 'line',
    'info_shape': {
      'id_shape': globals.selectedShapeID.toString(),
      'line': lseg,
    }
  };
 } 
http.Response response;
    try {
      //encode Map to JSON
      print("encode Map to JSON");
      var body = json.encode(data);
      print(body);
      response =
        await http.put(url,
          headers: {
            "Content-Type": "application/json"
          },
          body: body
        ).catchError((error) => print(error.toString()));

    } catch (e) {
      print(e);
    }
    return response;
  }

Flutter 请求数据库

Flutter put request for Database

json

put

psql

server

flutter