(Objective-C) Invalidating Dependent Variables When Inputs Change

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This example demonstrates how HttpCurl automatically updates the execution plan when a known variable is cleared or changed.

After a multi-step execution plan runs successfully, variables such as site_id and drive_id may become known. Later calls to DoYourThing can reuse those values, resulting in a shorter execution plan.

However, if an input variable is cleared using ClearVar, or changed using SetVar, any variables that depend on that value are automatically invalidated. This ensures that stale values are not reused.

For example, if site_name changes, then the previously resolved site_id is no longer valid. Because drive_id depends on site_id, it is also invalidated. The next execution plan is rebuilt to resolve the dependency chain again using the new input value.

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

For more information, see https://www.chilkatsoft.com/curl_dependency_engine.asp

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#import <CkoHttpCurl.h>
#import <NSString.h>
#import <CkoJsonObject.h>

BOOL success = NO;

CkoHttpCurl *httpCurl = [[CkoHttpCurl alloc] init];

// The target curl command we ultimately want to execute.
// It requires drive_id.
NSString *targetCurl = @"curl -X GET https://graph.microsoft.com/v1.0/drives/{{drive_id}}/root/children";

// Define a helper function that produces drive_id.
// This requires site_id.
NSString *fnName = @"getDrives";
[httpCurl AddFunction: fnName curl: @"curl -X GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives"];
[httpCurl AddOutput: fnName jsonPath: @"value[0].id" varName: @"drive_id"];

// Define another helper function that produces site_id.
// This requires site_name.
fnName = @"getSite";
[httpCurl AddFunction: fnName curl: @"curl -X GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}"];
[httpCurl AddOutput: fnName jsonPath: @"id" varName: @"site_id"];

// site_name is the starting known value.
[httpCurl SetVar: @"site_name" varValue: @"test"];

// Configure OAuth2 authentication.
CkoJsonObject *jsonOAuth2 = [[CkoJsonObject alloc] init];
jsonOAuth2.EnableSecrets = YES;
[jsonOAuth2 UpdateString: @"oauth2.client_id" value: @"!!sharepoint|oauth2|client_id"];
[jsonOAuth2 UpdateString: @"oauth2.client_secret" value: @"!!sharepoint|oauth2|client_secret"];
[jsonOAuth2 UpdateString: @"oauth2.scope" value: @"https://graph.microsoft.com/.default"];
[jsonOAuth2 UpdateString: @"oauth2.token_endpoint" value: @"!!sharepoint|oauth2|token_endpoint"];
[httpCurl SetAuth: jsonOAuth2];

// -----------------------------------------------------------------------------
// First execution plan:
// site_id and drive_id are not known yet, so the full dependency chain is needed.
// -----------------------------------------------------------------------------
CkoJsonObject *planJson = [[CkoJsonObject alloc] init];
planJson.EmitCompact = NO;

NSLog(@"%@",@"Execution plan before first call:");
success = [httpCurl ExaminePlan: targetCurl json: planJson];
NSLog(@"%@",[planJson Emit]);

// Expected:
// 
// {
//   "plan": [{
//     "function": "getSite",
//     "inputs": ["site_name"],
//     "outputs": ["site_id"]
//   },{
//     "function": "getDrives",
//     "inputs": ["site_id"],
//     "outputs": ["drive_id"]
//   },{
//     "function": "targetCurl",
//     "inputs": ["drive_id"],
//     "outputs": []
//   }]
// }

success = [httpCurl DoYourThing: targetCurl];
if (success == NO) {
    NSLog(@"%@",httpCurl.LastErrorText);
    return;
}

NSLog(@"%@",@"After first call:");
NSLog(@"%@%@",@"site_id  = ",[httpCurl GetVar: @"site_id"]);
NSLog(@"%@%@",@"drive_id = ",[httpCurl GetVar: @"drive_id"]);

// -----------------------------------------------------------------------------
// Second execution plan:
// site_id and drive_id are now known, so only the target curl command is needed.
// -----------------------------------------------------------------------------
NSLog(@"%@",@"Execution plan after first call:");
success = [httpCurl ExaminePlan: targetCurl json: planJson];
NSLog(@"%@",[planJson Emit]);

// Expected:
// 
// {
//   "plan": [{
//     "function": "targetCurl",
//     "inputs": ["drive_id"],
//     "outputs": []
//   }]
// }

// -----------------------------------------------------------------------------
// Change the original input.
// Because site_id was produced from site_name, changing site_name invalidates site_id.
// Because drive_id depends on site_id, drive_id is also invalidated.
// -----------------------------------------------------------------------------

// Note: Make sure this site exists on in your SharePoint...
[httpCurl SetVar: @"site_name" varValue: @"anotherSite"];

NSLog(@"%@",@"After changing site_name:");
NSLog(@"%@%d",@"site_id defined?  ",[httpCurl VarDefined: @"site_id"]);
NSLog(@"%@%d",@"drive_id defined? ",[httpCurl VarDefined: @"drive_id"]);

// -----------------------------------------------------------------------------
// The execution plan is automatically rebuilt.
// Since site_id and drive_id were invalidated, the full dependency chain is needed again.
// -----------------------------------------------------------------------------
NSLog(@"%@",@"Execution plan after changing site_name:");
success = [httpCurl ExaminePlan: targetCurl json: planJson];
NSLog(@"%@",[planJson Emit]);

// Expected:
// 
// {
//   "plan": [{
//     "function": "getSite",
//     "inputs": ["site_name"],
//     "outputs": ["site_id"]
//   },{
//     "function": "getDrives",
//     "inputs": ["site_id"],
//     "outputs": ["drive_id"]
//   },{
//     "function": "targetCurl",
//     "inputs": ["drive_id"],
//     "outputs": []
//   }]
// }

success = [httpCurl DoYourThing: targetCurl];
if (success == NO) {
    NSLog(@"%@",httpCurl.LastErrorText);
    return;
}

NSLog(@"%@",@"After running again with the new site_name:");
NSLog(@"%@%@",@"site_id  = ",[httpCurl GetVar: @"site_id"]);
NSLog(@"%@%@",@"drive_id = ",[httpCurl GetVar: @"drive_id"]);

// -----------------------------------------------------------------------------
// Clearing a variable also invalidates values that depend on it.
// Here, clearing site_id also invalidates drive_id.
// -----------------------------------------------------------------------------
[httpCurl ClearVar: @"site_id"];

NSLog(@"%@",@"After clearing site_id:");
NSLog(@"%@%d",@"site_id defined?  ",[httpCurl VarDefined: @"site_id"]);
NSLog(@"%@%d",@"drive_id defined? ",[httpCurl VarDefined: @"drive_id"]);

NSLog(@"%@",@"Execution plan after clearing site_id:");
success = [httpCurl ExaminePlan: targetCurl json: planJson];
NSLog(@"%@",[planJson Emit]);

// Expected:
// 
// {
//   "plan": [{
//     "function": "getSite",
//     "inputs": ["site_name"],
//     "outputs": ["site_id"]
//   },{
//     "function": "getDrives",
//     "inputs": ["site_id"],
//     "outputs": ["drive_id"]
//   },{
//     "function": "targetCurl",
//     "inputs": ["drive_id"],
//     "outputs": []
//   }]
// }