Xbase++ Requires Chilkat v11.5.0+

curl with Variable Substitution in a JSON Request Body

See more CURL Examples

This example shows how to use variables inside a JSON request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates JSON, Chilkat automatically applies proper JSON escaping to each substituted value, ensuring the resulting JSON remains valid. Xbase++

LOCAL nSuccess
LOCAL oSbCurl
LOCAL oCurl
LOCAL oSbRawRequest

nSuccess := 0

//  Variable names are enclosed between {{ and }}
//  Important: The variable {{var_name}} should be placed inside the quotes.

//  This is correct:
//  curl -X POST https://api.example.com/messages \
//    -H "Content-Type: application/json" \
//    -d '{"text":"{{message}}"}'

//  This is incorrect:
//    -d '{"text":{{message}}}'

oSbCurl := CreateObject("Chilkat.StringBuilder")
oSbCurl:AppendLn("curl -X POST https://api.example.com/messages \")
oSbCurl:AppendLn('  -H "Content-Type: application/json" \')
oSbCurl:AppendLn('  -d '{"text":"{{message}}"}'')

oCurl := CreateObject("Chilkat.HttpCurl")

//  In this example, the value we'll provide for the "message" variable
//  will contain chars that require JSON escaping.
oCurl:SetVar("message", 'He said "Hello, world!"')

//  To demonstrate how the variables are replaced, this example does not execute the curl command. 
//  Instead, it generates the raw HTTP request that would be sent if the curl command were run.
oSbRawRequest := CreateObject("Chilkat.StringBuilder")
nSuccess := oCurl:ToRawRequest(oSbCurl:GetAsString(), oSbRawRequest)
IF (nSuccess == 0)
    ? oCurl:LastErrorText
    oSbCurl:destroy()
    oCurl:destroy()
    oSbRawRequest:destroy()
    RETURN
ENDIF

? oSbRawRequest:GetAsString()

//  The output is shown below.
//  Notice that the quote chars around "Hello World!" are properly JSON escaped.

//  POST /messages HTTP/1.1
//  Host: api.example.com
//  Content-Type: application/json
//  Content-Length: 36
//  
//  {"text":"He said \"Hello, world!\""}

oSbCurl:destroy()
oCurl:destroy()
oSbRawRequest:destroy()