(Visual FoxPro) curl with Variable Substitution in a JSON Request Body

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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.

Note: This example requires Chilkat v11.5.0 or greater.

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LOCAL lnSuccess
LOCAL loSbCurl
LOCAL loCurl
LOCAL loSbRawRequest

lnSuccess = 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}}}'

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

loCurl = CreateObject('Chilkat.HttpCurl')

* In this example, the value we'll provide for the "message" variable
* will contain chars that require JSON escaping.
loCurl.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.
loSbRawRequest = CreateObject('Chilkat.StringBuilder')
lnSuccess = loCurl.ToRawRequest(loSbCurl.GetAsString(),loSbRawRequest)
IF (lnSuccess = 0) THEN
    ? loCurl.LastErrorText
    RELEASE loSbCurl
    RELEASE loCurl
    RELEASE loSbRawRequest
    CANCEL
ENDIF

? loSbRawRequest.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!\""}

RELEASE loSbCurl
RELEASE loCurl
RELEASE loSbRawRequest