我正在使用它URL从 Quandl 网站获取一些内容：
https://www.quandl.com/api/v3/datasets/FRED/PAYEMS.csv?exclude_column_names=true&rows=1&api_key=my_api_key
Quandl 服务器响应上述请求返回如下值：
2016-08-01, 144598.0
我需要使用 in 的值，所以：144598.0MQL4 Script
Q1。如何从上面的 URL 中获取要在MQL4脚本中使用的内容？
来自 SO ( https://stackoverflow.com/users/3666197/user3666197) 的一位非常有帮助的用户提供了以下内容script（原始发现于MQL4：从 CSV 读取单个值）（我自己添加了几个部分）来帮助我实现这一点，但是，我无法让它工作：
// Code created with the help of Stack Overflow question
// https://stackoverflow.com/questions/39279634/mql4-read-single-value-from-csv/39284875#39284875
// Question by p.luck:
// https://stackoverflow.com/users/5551849/p-luck
// Answer by user3666197:
// https://stackoverflow.com/users/3666197/user3666197
void OnStart()
{
string cookie = NULL,
headers;
char post[],
result[];
int res;
/* TODO: *
* Must allow MT4 to access the server URL, *
* you should add URL "https://www.quandl.com/api/v3/datasets/FRED/PAYEMS.csv" *
* in the list of allowed URLs *
* ( MT4 -> Tools -> Options -> [Tab]: "Expert Advisors" ): */
string aDataSOURCE_URL = "https://www.quandl.com/api/v3/datasets/FRED/PAYEMS.csv";
string aDataSOURCE_API = "?exclude_column_names=true&rows=1&api_key=my_api_key";
//-- Create the body of the POST request for API specifications and API-authorization
ArrayResize( post,
StringToCharArray( aDataSOURCE_API, // string text |--> [in] String to copy.
post, // uchar &array[] <--| [out] Array of uchar type.
0, // int start = 0 |--> [in] Position from which copying starts. Default - 0.
WHOLE_ARRAY, // int count = -1 |--> [in] Number of array elements to copy. Defines length of a resulting string. Default value is -1, which means copying up to the array end, or till terminating '\0'. Terminating zero will also be copied to the recipient array, in this case the size of a dynamic array can be increased if necessary to the size of the string. If the size of the dynamic array exceeds the length of the string, the size of the array will not be reduced.
CP_UTF8 // uint cp = CP_ACP |--> [in] The value of the code page. For the most-used code pages provide appropriate constants.
)
- 1
);
//-- Reset the last error code
ResetLastError();
//-- Loading a html page from Quandl
int timeout = 5000; //-- Timeout below 1000 (1 sec.) is not enough for slow Internet connection
res = WebRequest( "POST", // const string method |--> [in] HTTP method.
aDataSOURCE_URL, // const string URL |--> [in] URL.
cookie, // const string cookie |--> [in] Cookie value.
NULL, // const string referrer |--> [in] Value of the Referer header of the HTTP request.
timeout, // int timeout |--> [in] Timeout in milliseconds.
post, // const char &data |--> [in] Data array of the HTTP message body
ArraySize( post ), // int data_size |--> [in] Size of the data[] array.
result, // char &result <--| [out] An array containing server response data.
headers // string &result_headers <--| [out] Server response headers.
);
//-- Check errors
if ( res == -1 )
{ Print( "WebRequest Error. Error code = ", GetLastError() ); //-- Perhaps the URL is not listed, display a message about the necessity to add the address
MessageBox( "Add the address '" + aDataSOURCE_URL + "' in the list of allowed URLs on tab 'Expert Advisors'", "Error", MB_ICONINFORMATION );
}
else //-- Load was successfull
{
PrintFormat( "The data has been successfully loaded, size = %d bytes.", ArraySize( result ) );
//-- parse the content ---------------------------------------
/*
"2016-08-01, 144598.0"
*/
//-- consume the content -------------------------------------
//...
}
}
我已将URLof添加
https://www.quandl.com/api/v3/datasets/FRED/PAYEMS.csv
到 in 的列表allowed URLs中MT4。
如果我启用并将名为 ( )的名称AutoTrading拖到a of 上，我会在以下内容中收到这些消息：scripttutorial7chartUSDCAD,M1Experts tab
Script tutorial7 USDCAD,M1: loaded successfulytutorial7 USDCAD,M1: initializedtutorial7 USDCAD,M1: The data has been successfully loaded, size = 0 bytestutorial7 USDCAD,M1: uninit reason 0
当然如果“ The data has successfully loaded”不应该说“ size = 0 bytes”？
script如果我只是将它直接复制并粘贴到它中，MetaQuotes Language Editor这是否可以正常工作compile？
除了添加URL到allowed URLsinMT4并将此代码复制并粘贴到 a之外script，还有什么我必须做的吗？
如果是这样，怎么做？
我正在运行上面的代码，而Script 不是Expert Advisor; 这个可以吗？
Q2。我可以将获取的 144598.0 值设置为脚本中的变量吗？
我需要制作一个变量value，144598.0以便可以将它与另一个进行比较value。
像这样的工作：
void OnStart()
{
... // above code which fetches the value from the .csv URL
double x = 155876.0 // value manually typed in
y = 144598.0 // value fetched from the .csv URL using the above code
// ignores column 1 consisting of 2016-08-01
if ( x > y ) {
// execute code
}
else {
// execute other code
}
}