如何避免GSP中的常规代码？

Question

I've to display check box checked or not based on some logic which is more than 4 lines of groovy code ... I don't like to write it in GSP page..is there any taglib or some way I can extract the logic out of GSP page. where I could access model boject and request objects.

Answer 1

A TagLib is a good palce to put your logic, you can pass what you need as attributes and do your test:

class MyTagLib {
  static namespace = "my"

  def somecheckbox= { attrs ->
      def model = attrs.remove('model')
      if() { //tests goes here
          //you can also test if you need to mark the checkbox as checked
          if() {
              attrs.checked = "checked"
          }
          out << g.checkbox(attrs: attrs) //remaining attrs will be applied to the checkbox
      }
  }

}

myview.gsp

<my:somecheckbox model="${model}" name="checkboxname" value="${checkboxValue}" />

Answer 2

You have (at least) 3 options:

Model attribute

If you're only doing the complex logic for a single page or a single controller, do the logic in the controller method and pass the boolean result to the view through a boolean:

// in your controller
def myAction() {
    [shouldDrawCheckbox: shouldDrawCheckBox(...)]
}

private boolean shouldDrawCheckBox(/* info for decision making */) {
    // decision making
}

Service method

If you're going to access this identical logic from several controllers, you can extract the shouldDrawCheckBox method into a service and again pass the result through the models.

class MyController {
    def myService

    def myAction() {
        [shouldDrawCheckbox: myService.shouldDrawCheckbox(...)]
    }
}

class MyService {
    boolean shouldDrawCheckBox(...) {
        // logic!
    }
}

Custom Taglib

If you want to avoid passing the decision through the model, or if the logic is more generally applicable, you can create a custom taglib.

class MyTaglib {
    static namespace = "my"

    def myCheckbox = { attrs ->
        // extract decision info from the attrs
        // perform logic with info
        if (shouldDrawCheckbox)
            out << g.checkbox(attrs: attrs)
        }
    }
}

In your view:

<my:myCheckbox whateverYourAttribsAre="value" name="..." value="..."/>

Answer 3

Ideally the logic should go to the controller which renders the gsp and sets a flag in the model object. If the gsp is a child of a template, then the flag has to pass through. DOM manipulations in view layer is not ideal when we have appropriate binding framework available in grails.

Answer 4

Use the g: namespace. http://grails.org/doc/2.2.x/ref/Tags/checkBox.html

<g:checkBox name="myCheckbox" value="${condition}" />

It doesn't get any simpler then this. All the logic should be done inside the controller.

All the data you need on a page can be passed by the controller. Just return a Map .

class MyController {
    def index() {
        def someCondition = true
        [request:request, condition:someCondition]
    }
}