How can you dynamically create input forms in an elevator

Question

I am working on my first Lift project and need to create forms on the fly. To be more precise, I have some operations that are represented by objects that have a list of parameters associated with them - some of them are strings, some numbers, some logical, some files. I need to pass the specific values ​​of the operation object for its parameters through the form. Currently, I just move the list of parameters and generate the form directly as XML, but I know that this is a very bad style - I cannot bind input values, I cannot bind an action to submit, I cannot apply validation. I am stuck skipping query parameters, but I want to fix it. Unfortunately, I have to figure out how to do this, so any help would be greatly appreciated. The whole example that I find always contains a fixed number of input parameters.

Here is some code. Hope this is clear enough (and I'm really ashamed to show this publicly :-))

def operationForm(): NodeSeq = { val operationCode = S.param("operation").openOr("") val operationVariant = S.param("operationVariant").openOr("") if (operationCode != "" && !operationVariant.isEmpty) { val operation = LighthouseDAOs.operationsRegistry.findByCode(operationCode) val params: List[Parameter] = if (operationVariant == "default") { operation.getParameters.toList } else { operation.getParameters.filter(p => p.getVariant == operationVariant).toList } <lift:surround with="closableBox" at="content"> <form id="viewOperation" post={"/Deployment/" + S.param("location") + "/" + S.param("deployment")} method="post"> {params.map(p => getInputElem(p))} <input type="submit" style="width: 150px;" value="Execute operation"/> <input type="hidden" name="executeOperation" value="true"/> </form> </lift:surround> } else { <span></span> } } private def getOperationVariants(operation: Operation): Set[String] = { operation.getParameters.map(_.getVariant).toSet } def operationVariants(deployment: Deployment): NodeSeq = { val operationCode = S.param("operation").openOr("") if (operationCode != "") { val operation = LighthouseDAOs.operationsRegistry.findByCode(operationCode) val variants = getOperationVariants(operation) if (variants.size > 1) { <lift:surround with="closableBox" at="content"> <table cellspacing="0" cellpadding="0" border="0"> <tr> <th style="width: 160px;">Operation {operation.getLongName} variants</th> </tr>{variants.map(v => { <tr> <td> <a href={Path.path + "Deployment/" + encode(deployment.getLocation) + "/" + encode(deployment.getDeployedComponent.getCode) + "?operation=" + encode(operation.getCode) + "&operationVariant=" + encode(v)}> {v} </a> </td> </tr> })} </table> </lift:surround> } else { <span></span> } } else { <span></span> } } def getInputElem(param: Parameter): Node = { if (param.getChoice != null) { <div> <label for={param.getName}> {param.getName} </label> <select id={param.getName} name={param.getName}> {param.getChoice.flatMap(c => <option value={c}> {c} </option>)} </select> </div> } else { val paramType = param.getType match { case Parameter.PASSWORD => "password" case Parameter.BOOLEAN => "checkbox" case Parameter.CLOB => "file" case _ => "text" } <div> <label for={param.getName}> {param.getName} :</label> <input type={paramType} id={param.getName} name={param.getName} stype="width: 300px;"> {param.getDefaultValue} </input> </div> } } def executeOperation(deployment: Deployment): Elem = { val operationCode = S.param("operation").openOr("") val operationVariant = S.param("operationVariant").openOr("") if (S.param("executeOperation").openOr("false") == "true") { val op = LighthouseDAOs.operationsRegistry.findByCode(operationCode) val params = op.getParameters LogLH3.info("Executing operation: " + op.getLongName) val operationInstallation = new OperationInstallation(); operationInstallation.setInstallationLocation(deployment); operationInstallation.setInstalledOperation(op); val operationCall = new OperationCall(operationInstallation); if (operationVariant != "" && operationVariant != "default") operationCall.setVariant(operationVariant) params.filter(p => p.getVariant == operationVariant).foreach(p => operationCall.addParameterValue(op.createParameterValue(p.getName, S.param(p.getName).openOr("")))) try { LighthouseDAOs.operationInstallationRegistry.execute(operationCall) S.notice("Operation " + op.getLongName + " was executed successfully.") } catch { case e: Exception => S.error(e.getMessage) } } <span></span> } 

For recording only, I use Lift 2.2 and Scala 2.8.1

Answer 1

You can improve this example and make it a little more constructive, but here is the main idea. You will need to wrap this in some form, of course.

Basically, you have a template and its contents are replaced with something dynamically created using CSS selector binding.

In your template:

 <div class="lift:MyForm.render"> Form will go here </div> 

Excerpt:

 class MyForm extends Snippet { def render = { val fields = List("a", "b", "c") var params: Map[String, String] = ... //or whatever def setf(key: String)(value: String) = params = params.updated(key, value) def getf(key: String)() = params.get(key) "*" #> fields map { field => <p> <label>{field}</label>{SHtml.text(getf(field) _, setf(field) _)} </p> } } }