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Formulas Tutorials

#7 Formulas using REST or WebApi Calls

Formulas using WebAPI and REST calls

Formulas can retrieve data from WebAPIs and REST. We have various examples of this on other pages, so this page will just repeat the examples from those page.

Get Data for a Field from a Web API

Get value for a field from a WebAPI

This formula is very advanced, and will initialize a fields value (if empty) from a WebAPI call.
Click on the (Σ) button above to see the edit-UI with the formula.

Formulas of `FormulasWebApiText.Title`

Field.Settings.Disabled (Formula-Target: Field.Settings.Disabled)

function v1 (data, context) {
  // Only enable once data has been loaded
  return !data.Title;
}

Field.Value (Formula-Target: Field.Value)

function v1 (data, context) {
  // for demo reasons, don't do this till start is toggled.
  if (!data.Start) return data.value;

  // If it has a value, keep it, don't look for another
  if (data.value) return data.value;

  // If data had been stored in the cache by the api-call, return it
  if (context.cache.data) return context.cache.data;
  
  // Prevent the API call from running twice
  if (context.cache.alreadyRun) return data.value;
  context.cache.alreadyRun = true;
  // Call the sxc web-api controller from other tutorials
  context.sxc.webApi.fetchJson('app/auto/api/basic/hello')
    .then(data => {
      console.log('got data', data);// log for demo reasons
      context.cache.data = data;  // set cache for next formula cycle
      context.form.runFormulas(); // trigger the next formula cycle
    });
  // After starting the web-api call, return the current empty value
  return data.value;
}

Get DropDown options from a WebAPI

Get dropdown options from WebAPI

This is an advanced formula which will call a WebApi to get the possible values in a drop down.
Click on the (Σ) button above to see the edit-UI with the formula.

Formulas of `FormulasDropdownWebApi.Dropdown`

Field.Settings.DropdownValues (Formula-Target: Field.Settings.DropdownValues)

function v1 (data, context) {
  // If it has a value, keep it, don't look for another
  if (data.value) return data.value;

  // If data had been stored in the cache by the api-call, return it
  if (context.cache.data) return context.cache.data;
  
  // Prevent the API call from running twice
  if (context.cache.alreadyRun) return data.value;
  context.cache.alreadyRun = true;

  // Call the sxc web-api controller from other tutorials
  context.sxc.webApi.fetchJson('app/auto/api/formulas/OptionsFromBackend')
    .then(data => {
      console.log('got data', data);// log for demo reasons
      // The result is a dictionary, so we convert to lines
      const lines = Object.keys(data)
        .map(k => k + ":" + data[k])
        .join('\n');
      context.cache.data = lines;  // set cache for next formula cycle
      context.form.runFormulas(); // trigger the next formula cycle
    });
}

Source Code of /api/FormulasController.cs

Below you'll see the source code of the file. Note that we're just showing the main part, and hiding some parts of the file which are not relevant for understanding the essentials. Click to expand the code

// Add namespaces for security check in Oqtane & DNN despite differences in .net core/.net Framework
// If you only target one platform, you can remove the parts you don't need
#if NETCOREAPP
using Microsoft.AspNetCore.Authorization; // .net core [AllowAnonymous] & [Authorize]
using Microsoft.AspNetCore.Mvc;           // .net core [HttpGet] / [HttpPost] etc.
#else
using System.Web.Http;                    // .net 4.5 [AllowAnonymous] / [HttpGet]
using DotNetNuke.Web.Api;                 // [DnnModuleAuthorize] & [ValidateAntiForgeryToken]
#endif
using System.Collections.Generic;          // To use the Dictionary

[AllowAnonymous]                          // all commands can be accessed without a login
public class FormulasController : Custom.Hybrid.Api14 // see https://r.2sxc.org/CustomWebApi
{
  [HttpGet]                               // [HttpGet] says we're listening to GET requests
  public object OptionsFromBackend()
  {
    var results = new Dictionary<string, string>() {
      { "first", "First option from WebApi" },
      { "second", "Second option from WebApi"},
      { "third", "3rd option" }
    };
    return results;
  }

}

// The next line is for 2sxc-internal quality checks, you can ignore this
// 2sxclint:disable:no-dnn-namespaces - 2sxclint:disable:no-web-namespace

Formulas using parameters