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Beginner JSON question
Posted: Sat Jun 27, 2015 11:26 am
by firace
I'm somewhat struggling with the JSON commands (major understatement!)...
The below code returns the top Google result for a keyword, in JSON format.
How can I extract the URL from that JSON result?
Thanks!
Code: Select all
Procedure.s GetHTTPText(URL$, TimeOut=5000)
Protected BufferSize = $1000, *Buffer = AllocateMemory(BufferSize)
Protected ServerName$ = GetURLPart(URL$, #PB_URL_Site)
Protected ConnectionID = OpenNetworkConnection(ServerName$, 80)
If ConnectionID
SendNetworkString(ConnectionID, "GET "+URL$+" HTTP/1.0" +#LFCR$+#LFCR$)
Time = ElapsedMilliseconds()
Repeat
Delay(10)
Event = NetworkClientEvent(ConnectionID)
If Event = #PB_NetworkEvent_Data
Repeat
Size = ReceiveNetworkData(ConnectionID, *Buffer, BufferSize)
String$ + PeekS(*Buffer, Size, #PB_Ascii)
Until Not Size
Inhalt = FindString(String$, #LFCR$, 1)
If Inhalt
String$ = Mid(String$, Inhalt+3)
EndIf
EndIf
Until ElapsedMilliseconds()-Time > TimeOut Or String$
CloseNetworkConnection(ConnectionID)
EndIf
FreeMemory(*Buffer)
ProcedureReturn String$
EndProcedure
InitNetwork()
S$ = GetHTTPText("http://ajax.googleapis.com/ajax/services/search/web?v=1.0&rsz=1&q=alcatraz" )
Debug S$
ParseJSON(1, S$)
Debug JSONType(JSONValue(1))
Re: Beginner JSON question
Posted: Sat Jun 27, 2015 1:11 pm
by freak
The JSON commands let you walk the nested JSON data to get to individual values. For example like this:
Code: Select all
ParseJSON(1, S$)
response = JSONValue(1)
responseData = GetJSONMember(response, "responseData")
results = GetJSONMember(responseData, "results")
result = GetJSONElement(results, 0)
url = GetJSONMember(result, "url")
Debug GetJSONString(url)
However, as you can see this can become cumbersome. If you know that the JSON will be of the same structure every time (as it is with such web APIs), i find it easier to map the results directly into PB structures and work with that.
Basically you define nested structures to match the JSON data like this:
- JSON Arrays (with "[]") can be mapped to a PB Array or List
- JSON Objects (with "{}") can be mapped to either a PB Map or a sub-structure.
-
Everything else can be mapped to a single value of appropriate type
Once this is done, you can use ExtractJSONStructure() to read the entire JSON data into the structure.
Example:
Code: Select all
Structure SearchResult
GsearchResultClass.s
unescapedUrl.s
url.s
visibleUrl.s
cacheUrl.s
title.s
titleNoFormatting.s
content.s
EndStructure
Structure CursorPage
start.s
label.i
EndStructure
Structure SearchCursor
resultCount.s
Array pages.CursorPage(1)
estimatedResultCount.s
currentPageIndex.i
moreResultsUrl.s
searchResultTime.s
EndStructure
Structure ResponseData
Array results.SearchResult(1)
cursor.SearchCursor
EndStructure
Structure Response
responseData.ResponseData
responseDetails.s
responseStatus.i
EndStructure
ParseJSON(1, S$)
ExtractJSONStructure(JSONValue(1), @response.Response, Response)
Debug response\responseStatus
Debug response\responseData\results(0)\titleNoFormatting
Debug response\responseData\results(0)\url
Re: Beginner JSON question
Posted: Sat Jun 27, 2015 1:43 pm
by falsam
Thank freak, very good demonstration
I often use
ComposeJSON() to review the content of JSON.
Example:
Debug ComposeJSON(1, #PB_JSON_PrettyPrint)
Re: Beginner JSON question
Posted: Sat Jun 27, 2015 2:15 pm
by firace
Thank you so much freak, that was most helpful!
Re: Beginner JSON question
Posted: Thu Jul 16, 2015 2:22 am
by destiny
freak, very useful if json data has the same structure every time!