Delphi XE2 を使用して Web サイトから JSON を解析しようとしましたが、このスレッドで提案されているコードは hereです。回答者の投稿に表示されているとおりにコードを実装すると機能しますが、ほとんど同じものを実装すると、次の行でアクセス違反が発生します。
LParts:=LJsonObj.Get('parts').JsonValue;
そして、(実行時に) 毎回 AV で失敗します (正常にコンパイルされますが、実行されません)。コードを簡略化しました。以下は、動作すると思われるスニペットです。結局のところ、これは他の動作中のコードのコピー アンド ペーストです。
誰かが以下を見て、なぜ私のものが機能しないのに、参照された投稿のコードが機能するのかを教えていただければ、本当に感謝しています。デバッグすると、動作しているように見え、デバッグ情報がほとんどないため、私は主に困惑しています。
program ReadJSONConsoleApp;
{$APPTYPE CONSOLE}
{$R *.res}
uses
DBXJSON,
System.SysUtils;
Const
StrJson=
'{' +
' "response" : [ {' +
' "distributor" : {' +
' "id" : 1538,' +
' "name" : "Arrow Electronics",' +
' "authorized" : true,' +
' "logoUrl" : "this is normally a URL but I cut it out"' +
' },' +
' "parts" : [ {' +
' "manufacturer" : "National Semiconductor",' +
' "part" : "LM741WG/883",' +
' "description" : "OP Amp Single GP ±22V 10-Pin CFPAK Tray",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 65.0,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 88,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "National Semiconductor",' +
' "part" : "LM741W/883",' +
' "description" : "OP Amp Single GP ±22V 10-Pin CPAK Rail",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 40.5,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 1464,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741CH",' +
' "description" : "OP Amp Single GP ±18V 8-Pin TO-99 Box",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 5.22,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 95,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741CN",' +
' "description" : "OP Amp Single GP ±18V 8-Pin PDIP Rail",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 0.3633,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 4320,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741H",' +
' "description" : "OP Amp Single GP ±22V 8-Pin TO-99 Box",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 5.22,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 3458,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741H",' +
' "description" : "OP Amp Single GP ±22V 8-Pin TO-99 Box",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 5.71,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 0,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741CN/NOPB",' +
' "description" : "OP Amp Single GP ±18V 8-Pin PDIP Rail",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 0.2977,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 6486,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741J",' +
' "description" : "OP Amp Single GP ±22V 8-Pin CDIP Rail",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 7.21,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 362,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741H/NOPB",' +
' "description" : "OP Amp Single GP ±22V 8-Pin TO-99 Box",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 5.22,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 1378,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741J/883",' +
' "description" : "OP Amp Single GP ±22V 8-Pin CDIP Rail",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 11.8,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 989,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741H/883",' +
' "description" : "OP Amp Single GP ±22V 8-Pin TO-99 Tray",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 15.74,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 4252,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }, {' +
' "manufacturer" : "Texas Instruments",' +
' "part" : "LM741CHNOPB",' +
' "description" : "OP Amp Single GP ±18V 8-Pin TO-99 Box",' +
' "price" : [ {' +
' "quantity" : 0,' +
' "price" : 5.22,' +
' "currency" : "USD"' +
' } ],' +
' "stock" : 785,' +
' "lastUpdated" : "2013-11-04 18:27:16 UTC"' +
' }' +
' } ]' +
' } ]' +
'}';
procedure ParseJson;
var
LJsonObj : TJSONObject;
LJPair : TJSONPair;
LParts : TJSONValue;
LPart : TJSONValue;
LItem : TJSONValue;
LIndex : Integer;
LSize : Integer;
begin
LJsonObj := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(StrJson),0) as TJSONObject;
try
LParts:=LJsonObj.Get('parts').JsonValue;
LSize:=TJSONArray(LParts).Size;
for LIndex:=0 to LSize-1 do
begin
LPart := TJSONArray(LParts).Get(LIndex);
LJPair := TJSONPair(LPart);
Writeln(Format('Part Name %s',[LJPair.JsonString.Value]));
for LItem in TJSONArray(LJPair.JsonValue) do
begin
if TJSONPair(LItem).JsonValue is TJSONFalse then
Writeln(Format(' %s : %s',[TJSONPair(LItem).JsonString.Value, 'false']))
else
if TJSONPair(LItem).JsonValue is TJSONTrue then
Writeln(Format(' %s : %s',[TJSONPair(LItem).JsonString.Value, 'true']))
else
Writeln(Format(' %s : %s',[TJSONPair(LItem).JsonString.Value, TJSONPair(LItem).JsonValue.Value]));
end;
end;
finally
LJsonObj.Free;
end;
end;
begin
try
ParseJson;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
Readln;
end.