我有一個這樣的 JSON：
{
"Content": [{
"Identifier": "AABBCC",
"Description": "test terfdfg",
"GenericProductIdentifier": "AABBCC",
"ProductFamilyDescription": "sampling",
"LifeCycleStatus": "ACTIVE",
"Price": {
"Value": 1.00,
"Quantity": 1000
},
"LeadTimeWeeks": "16",
"FullBoxQty": 200,
}],
"TotalElements": 1,
"TotalPages": 1,
"NumberOfElements": 1,
"First": true,
"Size": 1,
"Number": 0
}
在 Delphi 10.4 中，我試圖決議它，但我無法訪問 'Price' 中包含的值。
我寫了這樣的代碼：
var
vContent: TJSONArray;
vJson: TJSONObject;
vContentRow: TJSONObject;
i,j : Integer;
begin
Memo2.Lines.Clear;
if Memo1.Text = '' then
exit;
vJson := TJSONObject(TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(Memo1.Text),0));
try
vContent := TJSONArray(vJson.Get('Content').JsonValue);
for i := 0 to Pred(vContent.Count) do
begin
vContentRow := TJSONObject(vContent.Items[i]);
for j := 0 to Pred(vContentRow.Count) do
begin
Memo2.Lines.Add(' ' vContentRow.Get(j).JsonString.Value ' : ' vContentRow.Get(j).JsonValue.Value);
end;
end;
Memo2.Lines.Add(vContent.Value);
finally
end;
end;
讀取“價格”中包含的值的正確方法是什么？
uj5u.com熱心網友回復：
這是決議 JSON 的示例代碼：
uses
System.IOUtils, System.JSON, System.Generics.Collections;
procedure TForm1.Button1Click(Sender: TObject);
procedure GetPrices(const S: string);
var
V: TJsonValue;
O, E, P: TJsonObject;
A: TJsonArray;
begin
V := TJSONObject.ParseJSONValue(S);
if not Assigned(V) then
raise Exception.Create('Invalid JSON');
try
O := V as TJSONObject;
A := O.GetValue<TJsonArray>('Content');
for var I := 0 to A.Count - 1 do
begin
E := A.Items[I] as TJsonObject; // Element
P := E.GetValue<TJsonObject>('Price');
ShowMessage('Value: ' P.GetValue<string>('Value') ' ' 'Quantity: ' P.GetValue<string>('Quantity'));
end;
finally
V.Free;
end;
end;
var
S: string;
begin
S := TFile.ReadAllText('d:\json.txt'); // Retrieve it using some webservice
GetPrices(S);
end;
注意，你的 JSON 是無效的，正確的定義是：
{
"Content": [{
"Identifier": "AABBCC",
"Description": "test terfdfg",
"GenericProductIdentifier": "AABBCC",
"ProductFamilyDescription": "sampling",
"LifeCycleStatus": "ACTIVE",
"Price": {
"Value": 1.00,
"Quantity": 1000
},
"LeadTimeWeeks": "16",
"FullBoxQty": 200
}],
"TotalElements": 1,
"TotalPages": 1,
"NumberOfElements": 1,
"First": true,
"Size": 1,
"Number": 0
}
uj5u.com熱心網友回復：
你可以使用JSON libraryDelphi的。JSON庫具有JsonToObject class function可以直接將字串轉換為物件（物件結構）
看到這個： https ://docwiki.embarcadero.com/Libraries/Sydney/en/REST.Json.TJson.JsonToObject
您可以使用網路手動創建類結構： https ://jsontodelphi.com/
您創建的 JSON 的類結構是這樣的：
type
TPrice = class;
TPrice = class
private
FQuantity: Integer;
FValue: Double;
published
property Quantity: Integer read FQuantity write FQuantity;
property Value: Double read FValue write FValue;
end;
TContent = class
private
FDescription: string;
FFullBoxQty: Integer;
FGenericProductIdentifier: string;
FIdentifier: string;
FLeadTimeWeeks: string;
FLifeCycleStatus: string;
FPrice: TPrice;
FProductFamilyDescription: string;
published
property Description: string read FDescription write FDescription;
property FullBoxQty: Integer read FFullBoxQty write FFullBoxQty;
property GenericProductIdentifier: string read FGenericProductIdentifier write FGenericProductIdentifier;
property Identifier: string read FIdentifier write FIdentifier;
property LeadTimeWeeks: string read FLeadTimeWeeks write FLeadTimeWeeks;
property LifeCycleStatus: string read FLifeCycleStatus write FLifeCycleStatus;
property Price: TPrice read FPrice;
property ProductFamilyDescription: string read FProductFamilyDescription write FProductFamilyDescription;
public
constructor Create;
destructor Destroy; override;
end;
TRoot = class(TJsonDTO)
private
[JSONName('Content'), JSONMarshalled(False)]
FContentArray: TArray<TContent>;
[GenericListReflect]
FContent: TObjectList<TContent>;
FFirst: Boolean;
FNumber: Integer;
FNumberOfElements: Integer;
FSize: Integer;
FTotalElements: Integer;
FTotalPages: Integer;
function GetContent: TObjectList<TContent>;
protected
function GetAsJson: string; override;
published
property Content: TObjectList<TContent> read GetContent;
property First: Boolean read FFirst write FFirst;
property Number: Integer read FNumber write FNumber;
property NumberOfElements: Integer read FNumberOfElements write FNumberOfElements;
property Size: Integer read FSize write FSize;
property TotalElements: Integer read FTotalElements write FTotalElements;
property TotalPages: Integer read FTotalPages write FTotalPages;
public
destructor Destroy; override;
end;
現在，決議元素的代碼更簡單了。您只需要這樣的代碼即可訪問結構的不同屬性：
var
Root: TRoot;
begin
root := TJSON.JsonToObject<TRoot>(Memo1.Lines.Text);
lblid.Caption := 'TotalElements: ' Root.TotalElements.ToString;
lblvalue.Caption := 'TotalPages: ' Root.TotalPages.ToString;
lblcount.Caption := 'Identifier: ' Root.Content[0].Identifier;
lblfirstonclick.Caption := 'Description: ' Root.Content[0].Description;
lbllastonclick.Caption := 'Price/Quantity:' Root.Content[0].Price.Quantity.ToString;
//...
uj5u.com熱心網友回復：
試試這個，我為 TFDMemtable 做了一些幫手。使用簡單，每次有其他 JSON 時都無需決議。
const
JSONString =
'{
"Content": [{
"Identifier": "AABBCC",
"Description": "test terfdfg",
"GenericProductIdentifier": "AABBCC",
"ProductFamilyDescription": "sampling",
"LifeCycleStatus": "ACTIVE",
"Price": {
"Value": 1.00,
"Quantity": 1000
},
"LeadTimeWeeks": "16",
"FullBoxQty": 200,
}],
"TotalElements": 1,
"TotalPages": 1,
"NumberOfElements": 1,
"First": true,
"Size": 1,
"Number": 0
}';
begin
if not Memtable.FillDataFromString(JSONString) then begin
ShowMessages(Memtable.FieldByName('messages').AsString);
end else begin
Memtable.FillDataFromString(Memtable.FieldByName('Content').AsString);
ShowMessages(Memtable.FieldByName('Price').AsString);
end;
end;
====
unit BFA.Helper.MemTable;
interface
uses
System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.Memo.Types,
System.Rtti, FMX.Grid.Style, FMX.Grid, FMX.ScrollBox, FMX.Memo, FMX.Edit,
FMX.Controls.Presentation, FMX.StdCtrls, FireDAC.Stan.Intf,
FireDAC.Stan.Option, FireDAC.Stan.Param, FireDAC.Stan.Error, FireDAC.DatS,
FireDAC.Phys.Intf, FireDAC.DApt.Intf, System.Net.URLClient,
System.Net.HttpClient, System.Net.HttpClientComponent, Data.DB,
FireDAC.Comp.DataSet, FireDAC.Comp.Client, System.JSON, System.Net.Mime;
type
TFDMemTableHelper = class helper for TFDMemTable
procedure FillError(FMessage, FError : String);
function FillDataFromString(FJSON : String) : Boolean; //ctrl shift C
end;
implementation
{ TFDMemTableHelper }
function TFDMemTableHelper.FillDataFromString(FJSON: String): Boolean; //bug memoryleak fix at checking is Object / array soon
const
FArr = 0;
FObj = 1;
FEls = 2;
function isCheck(FString : String) : Integer; begin
Result := FEls;
var FCheck := TJSONObject.ParseJSONValue(FJSON);
if FCheck is TJSONObject then
Result := FObj
else if FCheck is TJSONArray then
Result := FArr;
FCheck.DisposeOf;
end;
var
JObjectData : TJSONObject;
JArrayJSON : TJSONArray;
JSONCheck : TJSONValue;
begin
var FResult := isCheck(FJSON);
try
Self.Active := False;
Self.Close;
Self.FieldDefs.Clear;
if FResult = FObj then begin
JObjectData := TJSONObject.ParseJSONValue(FJSON) as TJSONObject;
end else if FResult = FArr then begin
JArrayJSON := TJSONObject.ParseJSONValue(FJSON) as TJSONArray;
JObjectData := TJSONObject(JArrayJSON.Get(0));
end else begin
Self.FillError('FAILED PARSING JSON', 'THIS IS NOT JSON');
Result := False;
Exit;
end;
for var i := 0 to JObjectData.Size - 1 do begin
Self.FieldDefs.Add(
StringReplace(JObjectData.Get(i).JsonString.ToString, '"', '', [rfReplaceAll, rfIgnoreCase]),
ftString,
100000,
False
);
end;
Self.CreateDataSet;
Self.Active := True;
Self.Open;
try
if FResult = FArr then begin
for var i := 0 to JArrayJSON.Size - 1 do begin
JObjectData := TJSONObject(JArrayJSON.Get(i));
Self.Append;
for var ii := 0 to JObjectData.Size - 1 do begin
JSONCheck := TJSONObject.ParseJSONValue(JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON);
if JSONCheck is TJSONObject then
Self.Fields[ii].AsString := JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON
else if JSONCheck is TJSONArray then
Self.Fields[ii].AsString := JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON
else
Self.Fields[ii].AsString := JObjectData.Values[Self.FieldDefs[ii].Name].Value;
JSONCheck.DisposeOf;
end;
Self.Post;
end;
end else begin
Self.Append;
for var ii := 0 to JObjectData.Size - 1 do begin
JSONCheck := TJSONObject.ParseJSONValue(JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON);
if JSONCheck is TJSONObject then
Self.Fields[ii].AsString := JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON
else if JSONCheck is TJSONArray then
Self.Fields[ii].AsString := JObjectData.GetValue(Self.FieldDefs[ii].Name).ToJSON
else
Self.Fields[ii].AsString := JObjectData.Values[Self.FieldDefs[ii].Name].Value;
JSONCheck.DisposeOf;
end;
Self.Post;
end;
Result := True;
except
on E : Exception do begin
Result := False;
Self.FillError('Error Parsing JSON', E.Message);
end;
end;
finally
if FResult = FObj then
JObjectData.DisposeOf;
if FResult = FArr then
JArrayJSON.DisposeOf;
Self.First;
end;
end;
procedure TFDMemTableHelper.FillError(FMessage, FError : String);
begin
Self.Active := False;
Self.Close;
Self.FieldDefs.Clear;
Self.FieldDefs.Add('status', ftString, 200, False);
Self.FieldDefs.Add('messages', ftString, 200, False);
Self.FieldDefs.Add('data', ftString, 200, False);
Self.CreateDataSet;
Self.Active := True;
Self.Open;
Self.Append;
Self.Fields[0].AsString := FError;
Self.Fields[1].AsString := FMessage;
Self.Post;
end;
end.
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