Retrieving json data from web source and parsing it
lazarus / 38-Networking and Web Programming

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MikeJazz · 2017-02-28 19:21

Hi guys,
so I'm fairly new coding in general and I'm look for some help to get
me going with getting weather data from http://api.wunderground.com/ap
i/Your_Key/features/settings/q/query.format.

Now I've filled in the part after .../api/... to reflect what i want
to retrieve. Ang just typing it i to a browser i get what I'm looking
for.
Now the part I need help is sending of the url, and then parsing the
.json into variables that i can then use for my nefarious deeds.

I have added Synapse to my Lazarus and been playing with it, but to no
avail-

- Mike

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Phil · 2017-02-28 20:22

Quote from: MikeJazz on February 28, 2017, 08:21:24 pmHi guys,
so I'm fairly new coding in general and I'm look for some help to get
me going with getting weather data from http://api.wunderground.com/ap
i/Your_Key/features/settings/q/query.format.

Now I've filled in the part after .../api/... to reflect what i want
to retrieve. Ang just typing it i to a browser i get what I'm looking
for.
Now the part I need help is sending of the url, and then parsing the
.json into variables that i can then use for my nefarious deeds.

I assume you substituted your own key for "Your_Key", right?

With Synapse, you would use the THTTPSend class. Do a GET request with
the URL you want to send. If that succeeds, you can then read back the
JSON returned. Use FPC's JSON units to parse the JSON returned.

Look for examples for how to use Synapse and the JSON units.

On a related note, in case you're interested, the ndfd library used
with the example apps of Part 3 of the Dynamic Library article series
gets weather forecast data from NDFD. It's somewhat different from WU,
since it uses the NDFD SOAP service and thus the Web Service Toolkit
to make the request. And the data returned is XML, not JSON. But it's
there if you have a need for forecast data, in addition to WU
historical weather data.

https://macpgmr.github.io/

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sky_khan · 2017-02-28 20:48

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses  
fphttpclient, fpjson, jsonparser; procedure
TForm1.Button1Click(Sender: TObject);var  Http: TFPHttpClient; 
Content : string;  Json : TJSONData; begin 
Http:=TFPHttpClient.Create(Nil);  try   
 Content:=Http.Get('https://jsonplaceholder.typicode.com/users'); //
 this is just an example data     JSON:=GetJSON(Content);     try    
  // You may look http://wiki.freepascal.org/fcl-json to see what you
can do with TJSONData     finally       JSON.Free;     end;  finally 
 Http.Free;  end;end;

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BeniBela · 2017-02-28 22:43

My internet tools put it all together. E.g.:

Code: [Select]  uses xquery, xquery_json, synapseinternetaccess;
  query('json("http://api.wunderground.com/api/Your_Key/features/setti
ngs/q/query.format").forecast.txt_forecast.forecastday(1).fcttext').to
String

Or step by step:

Code: [Select]var
  forecasts: IXQValue;
begin
  forecasts := xqvalue('http://api.wunderground.com/api/Your_Key/featu
res/settings/q/query.format').retrieve().map('(.).forecast.txt_forecas
t.forecastday()');
  forecasts.get(1).getProperty('fcttext').toString;
  forecasts.get(2).getProperty('fcttext').toString;
  forecasts.get(3).getProperty('fcttext').toString;
  ...