Avoiding mixing client-side and server-side APIs

When working with client-side and server-side APIs, you must clearly understand the difference between the two API definitions to avoid using client-side APIs for server-side APIs, or vice-versa. All server-side APIs are prefixed with rbv_api. and all client-side APIs are prefixed with rbf_. Unlike client-side APIs, server-side APIs cannot be executed in the Web browser directly. If you must execute a server-side API in a client-side script, you must enclose the server-side API in an #EVAL[ ] block. The following section describes, with examples, how to avoid mixing client-side and server-side APIs.

The following script, when added to a page's script component, will cause a runtime error because an rbv_api. variable (a server-side API) is not recognized by a Web browser’s script:

<h2>Number of Clients: <span id='counter'></span></h2>
<script>
var count = rbv_api.selectNumber("select count(1) from client");
document.getElementById("counter").innerHTML = count;
</script>

The two ways to fix the above error are:

• Enclose the server-side API in an #EVAL[ ] block:

  <h2>Number of Clients: <span id='counter'></span></h2>
  <script>
  var count = #EVAL[ rbv_api.selectNumber("select count(1) from client"); ];
  document.getElementById("counter").innerHTML = count;
  </script>
  

  Note: When working with Script components, you can use the Test EVAL[] Block button to debug/develop server-side script.
• Use a client-side API instead of a server-side API:

  <h2>Number of A: <span id='counter'></span></h2>
  <script>
  rbf_selectNumber("select count(1) from a", function(value) {
   document.getElementById("counter").innerHTML = value; 
  });
  </script>
  

Typically, server-side API execution is faster and it is not subjected to a limit on the number of AJAX calls allowed per login session. A client-side API is used whenever user input can only be made available during runtime and not when the Web browser page is rendered.