Visual FoxPro Requires Chilkat v11.7.0+
Box: Reuse HttpCurl and Invalidate Cached IDs

Run the reusable setup once per HttpCurl object, then select names and execute the operation. The setup is repeated here only to make this published example independently runnable. Perform three operations with one configured object: cold file lookup, warm download without lookups, then another download to a different local path after clearing only file state. Functions and output rules are registered only once; their variables are evaluated when used.
See the Box API guide for setup and the complete workflow.
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LOCAL lnSuccess
LOCAL loCurl
LOCAL loSetupCommand
LOCAL lnSetupReplacements
LOCAL lcParentName
LOCAL lcFolderName
LOCAL lcFileName
LOCAL loAuthorizedCommand1
LOCAL lnHeaderReplacement1
LOCAL loWarmPlan
LOCAL loAuthorizedCommand2
LOCAL lnHeaderReplacement2
LOCAL loAuthorizedCommand3
LOCAL lnHeaderReplacement3
LOCAL loAuthorizedCommand4
LOCAL lnHeaderReplacement4
LOCAL loAuthorizedCommand5
LOCAL lnHeaderReplacement5

lnSuccess = 0

*  Requires Chilkat 11.7.0 or later and a previously unlocked Chilkat bundle.
*  See Global Unlock Sample.
*  Guide: Box API Guide.

lnSuccess = 0

*  BEGIN ONE-TIME SETUP
*  This block is repeated so each published example can run on its own.
*  In an application, run the setup example once and pass the SAME curl object
*  to operation code below. Do not recreate it for every operation.
*  See Reusable Box HttpCurl Setup.
loCurl = CreateObject('Chilkat.HttpCurl')
loCurl.SetVar("access_token","BOX_ACCESS_TOKEN")
loCurl.SetVar("parent_name","/")
*  Box's fixed root ID is an implementation detail; callers supply names.
loCurl.SetVar("parent_id","0")
loSetupCommand = CreateObject('Chilkat.StringBuilder')

*  Register findParent; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("findParent",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register findFolder; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/folders/{{parent_id}}/items?limit=1000&fields=id,type,name" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("findFolder",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register findFile; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/folders/{{folder_id}}/items?limit=1000&fields=id,type,name" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("findFile",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register findDestination; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("findDestination",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register getFileDetails; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}?fields=id,sha1,file_version" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("getFileDetails",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register getEnterprise; registration sends no request.
loSetupCommand.SetString('curl -X GET "https://api.box.com/2.0/users/me?fields=enterprise" -H "Authorization: Bearer ACCESS_TOKEN"')
lnSetupReplacements = loSetupCommand.Replace("ACCESS_TOKEN",loCurl.GetVar("access_token"))
lnSuccess = loCurl.AddFunction("getEnterprise",loSetupCommand.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  Register output rules once. Chilkat 11.7.0 evaluates {{name}} variables
*  when extracting each output, using the current value at that time.
lnSuccess = loCurl.AddOutput2("findParent","entries","name","{{parent_name}}",1,"id","parent_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput2("findFolder","entries","name","{{folder_name}}",1,"id","folder_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput2("findFile","entries","name","{{file_name}}",1,"id","file_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput2("findDestination","entries","name","{{destination_name}}",1,"id","destination_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput("getFileDetails","file_version.id","file_version_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput("getFileDetails","sha1","file_sha1")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

lnSuccess = loCurl.AddOutput("getEnterprise","enterprise.id","enterprise_id")
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    CANCEL
ENDIF

*  END ONE-TIME SETUP
*  The name lookups below assume each listing fits in one page (1000 items).
*  Parent and destination names select root children; folder_name selects a child
*  of parent_name. "/" selects the root parent. These are not arbitrary paths.

*  BEGIN OPERATION -- keep the configured object when reusing it.
*  Inputs are names. Retain cached IDs when the selected names have not changed.
lcParentName = "/"
lcFolderName = "images"
lcFileName = "penguins.jpg"
IF ((loCurl.GetVar("parent_name") <> lcParentName) OR ((lcParentName = "/") AND (loCurl.VarDefined("parent_id") = 0))) THEN
    loCurl.SetVar("parent_name",lcParentName)
    loCurl.ClearVar("parent_id")
    loCurl.ClearVar("folder_id")
    loCurl.ClearVar("file_id")
    loCurl.ClearVar("file_version_id")
    loCurl.ClearVar("file_sha1")
    IF (lcParentName = "/") THEN
        loCurl.SetVar("parent_id","0")
    ENDIF

ENDIF

IF (loCurl.GetVar("folder_name") <> lcFolderName) THEN
    loCurl.SetVar("folder_name",lcFolderName)
    loCurl.ClearVar("folder_id")
    loCurl.ClearVar("file_id")
    loCurl.ClearVar("file_version_id")
    loCurl.ClearVar("file_sha1")
ENDIF

IF (loCurl.GetVar("file_name") <> lcFileName) THEN
    loCurl.SetVar("file_name",lcFileName)
    loCurl.ClearVar("file_id")
    loCurl.ClearVar("file_version_id")
    loCurl.ClearVar("file_sha1")
ENDIF

loCurl.SetVar("local_path","qa_output/penguins.jpg")
*  Operation 1: get information by name. This resolves folder_id and file_id.
loCurl.ClearTargetOutput("*")
loAuthorizedCommand1 = CreateObject('Chilkat.StringBuilder')
loAuthorizedCommand1.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}?fields=id,name" -H "Authorization: Bearer {{access_token}}"')
lnHeaderReplacement1 = loAuthorizedCommand1.Replace("{{access_token}}",loCurl.GetVar("access_token"))
lnSuccess = loCurl.DoYourThing(loAuthorizedCommand1.GetAsString())
IF ((lnSuccess <> 1) OR (loCurl.StatusCode <> 200)) THEN
    ? "Box request failed. HTTP status: " + STR(loCurl.StatusCode)
    ? "Failure reason: " + STR(loCurl.FailReason)
    ? loCurl.ResponseBodyStr
    RELEASE loCurl
    RELEASE loSetupCommand
    RELEASE loAuthorizedCommand1
    CANCEL
ENDIF

*  Operation 2: keep the same object and IDs. Only the final download is needed.
loWarmPlan = CreateObject('Chilkat.JsonObject')
loWarmPlan.EmitCompact = 0
loAuthorizedCommand2 = CreateObject('Chilkat.StringBuilder')
loAuthorizedCommand2.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}/content" -H "Authorization: Bearer {{access_token}}" -L -o "{{local_path}}"')
lnHeaderReplacement2 = loAuthorizedCommand2.Replace("{{access_token}}",loCurl.GetVar("access_token"))
lnSuccess = loCurl.ExaminePlan(loAuthorizedCommand2.GetAsString(),loWarmPlan)
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    RELEASE loAuthorizedCommand1
    RELEASE loWarmPlan
    RELEASE loAuthorizedCommand2
    CANCEL
ENDIF

? loWarmPlan.Emit()
loCurl.ClearTargetOutput("*")
loAuthorizedCommand3 = CreateObject('Chilkat.StringBuilder')
loAuthorizedCommand3.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}/content" -H "Authorization: Bearer {{access_token}}" -L -o "{{local_path}}"')
lnHeaderReplacement3 = loAuthorizedCommand3.Replace("{{access_token}}",loCurl.GetVar("access_token"))
lnSuccess = loCurl.DoYourThing(loAuthorizedCommand3.GetAsString())
IF ((lnSuccess <> 1) OR (loCurl.StatusCode <> 200)) THEN
    ? "Box request failed. HTTP status: " + STR(loCurl.StatusCode)
    ? "Failure reason: " + STR(loCurl.FailReason)
    ? loCurl.ResponseBodyStr
    RELEASE loCurl
    RELEASE loSetupCommand
    RELEASE loAuthorizedCommand1
    RELEASE loWarmPlan
    RELEASE loAuthorizedCommand2
    RELEASE loAuthorizedCommand3
    CANCEL
ENDIF

*  Operation 3: explicitly invalidate file state, retaining the known folder.
*  Here we select the same name so this demonstration needs only one real file.
*  Substitute another filename to switch files in this folder.
*  The existing output rule reads the current file_name; do not register it again.
loCurl.ClearVar("file_id")
loCurl.ClearVar("file_version_id")
loCurl.ClearVar("file_sha1")
loCurl.SetVar("file_name","penguins.jpg")
loCurl.SetVar("local_path","qa_output/penguins-copy.jpg")
loAuthorizedCommand4 = CreateObject('Chilkat.StringBuilder')
loAuthorizedCommand4.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}/content" -H "Authorization: Bearer {{access_token}}" -L -o "{{local_path}}"')
lnHeaderReplacement4 = loAuthorizedCommand4.Replace("{{access_token}}",loCurl.GetVar("access_token"))
lnSuccess = loCurl.ExaminePlan(loAuthorizedCommand4.GetAsString(),loWarmPlan)
IF (lnSuccess <> 1) THEN
    ? loCurl.LastErrorText
    RELEASE loCurl
    RELEASE loSetupCommand
    RELEASE loAuthorizedCommand1
    RELEASE loWarmPlan
    RELEASE loAuthorizedCommand2
    RELEASE loAuthorizedCommand3
    RELEASE loAuthorizedCommand4
    CANCEL
ENDIF

? loWarmPlan.Emit()
loCurl.ClearTargetOutput("*")
loAuthorizedCommand5 = CreateObject('Chilkat.StringBuilder')
loAuthorizedCommand5.SetString('curl -X GET "https://api.box.com/2.0/files/{{file_id}}/content" -H "Authorization: Bearer {{access_token}}" -L -o "{{local_path}}"')
lnHeaderReplacement5 = loAuthorizedCommand5.Replace("{{access_token}}",loCurl.GetVar("access_token"))
lnSuccess = loCurl.DoYourThing(loAuthorizedCommand5.GetAsString())
IF ((lnSuccess <> 1) OR (loCurl.StatusCode <> 200)) THEN
    ? "Box request failed. HTTP status: " + STR(loCurl.StatusCode)
    ? "Failure reason: " + STR(loCurl.FailReason)
    ? loCurl.ResponseBodyStr
    RELEASE loCurl
    RELEASE loSetupCommand
    RELEASE loAuthorizedCommand1
    RELEASE loWarmPlan
    RELEASE loAuthorizedCommand2
    RELEASE loAuthorizedCommand3
    RELEASE loAuthorizedCommand4
    RELEASE loAuthorizedCommand5
    CANCEL
ENDIF

*  Changing parent_name invalidates parent_id, folder_id, and file state.
*  Changing folder_name invalidates folder_id and file state.
*  Changing destination_name invalidates destination_id.

RELEASE loCurl
RELEASE loSetupCommand
RELEASE loAuthorizedCommand1
RELEASE loWarmPlan
RELEASE loAuthorizedCommand2
RELEASE loAuthorizedCommand3
RELEASE loAuthorizedCommand4
RELEASE loAuthorizedCommand5