property |NSURL| : a reference to current application’s |NSURL|
property NSString : a reference to current application’s NSString
property NSURLSession : a reference to current application’s NSURLSession
property NSJSONSerialization : a reference to current application’s NSJSONSerialization
property NSMutableURLRequest : a reference to current application’s NSMutableURLRequest
property NSUTF8StringEncoding : a reference to current application’s NSUTF8StringEncoding
property NSURLSessionConfiguration : a reference to current application’s NSURLSessionConfiguration

property retData : missing value
property retCode : 0
property retHeaders : 0
property drecF : false

set reqURLStr to "http://jsonplaceholder.typicode.com/posts"
set aRESTres to callRestGETAPIAndParseResults(reqURLStr, 10) of me
–return retData of aRESTres

set aRESTcode to retCode of aRESTres
–return aRESTcode
–> 200

return retHeaders as record
–> {|content-type|:"application/json; charset=utf-8", Pragma:"no-cache", |x-powered-by|:"Express", |set-cookie|:"__cfduid=dd8b4572e0a59951cc7cf7a1120c368541554964103; expires=Fri, 10-Apr-20 06:28:23 GMT; path=/; domain=.typicode.com; HttpOnly", Server:"cloudflare", Via:"1.1 vegur", |content-encoding|:"gzip", Expires:"Wed, 01 May 2019 15:27:42 GMT", |cf-cache-status|:"HIT", |transfer-encoding|:"Identity", |cache-control|:"public, max-age=14400", |date|:"Wed, 01 May 2019 11:27:42 GMT", |access-control-allow-credentials|:"true", Connection:"keep-alive", |cf-ray|:"4d016861ac759413-NRT", Etag:"W/＼"6b80-Ybsq/K6GwwqrYkAsFxqDXGC7DoM＼"", Vary:"Origin, Accept-Encoding", |x-content-type-options|:"nosniff"}

on callRestGETAPIAndParseResults(reqURLStr as string, timeoutSec as integer)
　　set (my retData) to false
　　set (my retCode) to 0
　　set (my retHeaders) to {}
　　set (my drecF) to false
　　
　　set aURL to |NSURL|’s URLWithString:reqURLStr
　　set aRequest to NSMutableURLRequest’s requestWithURL:aURL
　　aRequest’s setHTTPMethod:"GET"
　　aRequest’s setValue:"gzip" forHTTPHeaderField:"Content-Encoding"
　　aRequest’s setValue:"application/json; charset=UTF-8" forHTTPHeaderField:"Content-Type"
　　
　　set aConfig to NSURLSessionConfiguration’s defaultSessionConfiguration()
　　set aSession to NSURLSession’s sessionWithConfiguration:aConfig delegate:(me) delegateQueue:(missing value)
　　set aTask to aSession’s dataTaskWithRequest:aRequest
　　
　　set hitF to false
　　aTask’s resume() –Start URL Session
　　
　　repeat (1000 * timeoutSec) times
　　　　if (my drecF) = true then
　　　　　　set hitF to true
　　　　　　exit repeat
　　　　end if
　　　　delay ("0.001" as real)
　　end repeat
　　
　　if hitF = false then error "REST API Timeout Error"
　　
　　return {retData:retData, retCode:retCode, retHeaders:retHeaders}
end callRestGETAPIAndParseResults

on URLSession:tmpSession dataTask:tmpTask didReceiveData:tmpData
　　parseSessionResults(tmpSession, tmpTask, tmpData) of me
　　set (my drecF) to true
end URLSession:dataTask:didReceiveData:

–ないとエラーになるので足した。とくに何もしていない
on URLSession:tmpSession dataTask:tmpTask willCacheResponse:cacheRes completionHandler:aHandler
　　—
end URLSession:dataTask:willCacheResponse:completionHandler: