class_="nest"

Example: Generating widgets dynamically (implicit syntax)

The following example uses the implicit syntax of class_="nest" to demonstrate how a parameterized value can be used to dynamically generate widgets.

<dynamic list="{str_to_lst('this,is,a,test';)}">
  <layout>
    <dynamic>
      <layout arrange_="v">
        <foreach var="{@list}">
          <widget class_="text" text_="{@var}"/>
        </foreach>
      </layout>
    </dynamic>
  </layout>
</dynamic>

Example: Generating widgets dynamically (explicit syntax)

The following example uses the explicit syntax of class_="nest" to demonstrate how multiple graphs are dynamically generated based on a parameterized value. This example generates three charts using a public weather data set (pub.demo.weather.wunderground.observed_daily) based on the column names defined in the metrics dynamic variable.

<defblock name="define_selections">
  <base table="pub.demo.weather.wunderground.observed_daily"/>
  <sel value="(zipcode='01001')"/>
  <sel value="between(date;20120901;20120930)"/>
</defblock>
<dynamic metrics="{lst('meantempi' 'meandewpti' 'meanpressurem')}">
  <widget class_="nest" insert_="define_selections">
    <dynamic>
      <layout align_="v">
        <foreach inc="{@metrics}" tally="@i">
          <widget class_="graphics" width_="800" height_="400" 
           metrics="{@inc}">
            <graphspec width="600" height="400">
              <chart type="line" samples="100000">
                <data x="date" y="{@metrics}"/>
              </chart>
            </graphspec>
          </widget>
        </foreach>
      </layout>
    </dynamic>
  </widget>
</dynamic>

Example: Generating widgets dynamically based on user interactions

The following example demonstrates how the nest widget can be used to generate widgets dynamically based on user interactions. A dropdownlist widget allows the user to select which graphs are displayed. The selections are saved as a list-value in the dynamic variable selected. When this variable changes, the nest widget updates automatically, creating a graphics widget for each item in the selected list-value.

<defblock name="define_selections">
  <base table="pub.demo.weather.wunderground.observed_daily"/>
  <sel value="(zipcode='01001')"/>
  <sel value="between(date;20120901;20120930)"/>
</defblock>
<defblock name="define_metrics" 
 metrics="{str_to_lst('meantempi,meandewpti,meanpressurem,precipi';)}">
  <table depth="1"/>
  <foreach row_val="{@metrics}" tally="@i">
    <willbe name="metric_{@i}" value="'{@row_val}'"/>
  </foreach>
  <transpose/>
</defblock>
<dynamic selected="{lst()}">
  <widget class_="dropdownlist" label_="Select desired metrics:" 
   insert_="define_metrics" listvalue_="@selected"/>
  <widget class_="nest" require_="{lst_len(@selected)>0}" invmode_="hide">
    <dynamic>
      <layout align_="v">
        <foreach metrics="{@selected}" tally="@i">
          <widget class_="graphics" insert_="define_selections" 
           width_="800" height_="400" metrics="{@metrics}">
            <graphspec width="600" height="400">
              <chart type="line" samples="100000">
                <data x="date" y="{@metrics}"/>
              </chart>
            </graphspec>
          </widget>
        </foreach>
      </layout>
    </dynamic>
  </widget>
</dynamic>

Using bind_ and to_

<library>
  <block name="get_cols" tablename="">
    <base table="{@table_name}"/>
    <columns/>
    <colord cols="name,label"/>
  </block>
  <defop name="selector" boolean="" count="" cols="" vals="">
    <set>
      <sel_expr>
        <for i="1" to="{@count}">
          <let col="{lst_pick({@cols};{@i})}" 
           val="{lst_pick({@vals};{@i})}" fun="has">
            <if test="{@i<=@count}">
              <then>
                <if test="{@i>1&@col<>''&@val<>''}">
                  <then>{@boolean}
                  </then>
                </if>
                <if test="{@col<>''&@val<>''}">
                  <then>({@col}={@val})
                  </then>
                </if>
              </then>
            </if>
          </let>
        </for>
      </sel_expr>
    </set>
    <if test="{@sel_expr<>''}">
      <then>
        <sel value="{@sel_expr}"/>
      </then>
    </if>
  </defop>
</library>
<dynamic cols="{mklst(3;'')}" funs="{mklst(3;'')}" 
 vals="{mklst(3;'')}" filter_cnt="1" table_name="" fld="" bool="|">
  <do onchange_="@table_name">
    <set cols="{mklst(3;'')}" vals="{mklst(3;'')}"/>
  </do>
  <layout arrange_="v">
    <widget class_="browser" value_="@table_name" 
     label_="Select Table" filter_="folder,table" accept_="table"/>
    <widget class_="dropdown" value_="@filter_cnt" label_="Filters">
      <table>1;2;3;
      </table>
    </widget>
    <widget name="bool_picker" class_="radio" value_="@bool" 
     invmode_="hide">
      <table>|,Or;&amp;,And
      </table>
    </widget>
    <widget class_="nest" bind_="cols,vals,table_name" 
     to_="cols,vals,table_name" require_="{@table_name<>'default.lonely'}">
      <dynamic>
        <layout arrange_="v">
          <for i="1" to="{@filter_cnt}">
            <layout arrange_="h">
              <widget class_="dropdown" value_="@cols.{@i}">
                <insert block="get_cols" tablename="{@table_name}"/>
              </widget>
              <widget class_="text" text_="Has the values" 
               deflabel_="Select"/>
              <widget class_="field" value_="@vals.{@i}"/>
            </layout>
          </for>
        </layout>
      </dynamic>
    </widget>
    <widget class_="button" type_="submit" text_="Submit"/>
    <widget class_="grid" update_="manual" type_="scroll" 
     label_="{@table_name}">
      <base table="{@table_name}"/>
      <selector boolean="{@bool}" count="{@filter_cnt}" 
       cols="{@cols}" vals="{@vals}"/>
    </widget>
    <widget class_="textbox" source_="ops" mode_="xml" 
     update_="manual">
      <base table="{@table_name}"/>
      <selector boolean="{@bool}" count="{@filter_cnt}" 
       cols="{@cols}" vals="{@vals}"/>
    </widget>
  </layout>
</dynamic>

Example: Exporting to an Excel workbook

The following example demonstrates how to use <widget class_="nest"> to export the contents of a nested <dynamic> to an Excel workbook. The target is specified by setting target_="xlsx". The export is triggered when the Export button is clicked, which increments the value of the dynamic variable r. Because the inner <dynamic> defines a variable updates that references the value of r, the nest widget is refreshed when the value of that variables changes.

<dynamic r="0">
  <widget class_="nest" target_="xlsx">
    <dynamic updates="{@r}">
      <widget class_="grid">
        <base table="pub.fin.econ.fed.fred"/>
        <sel value="date=19600201"/>
      </widget>
    </dynamic>
  </widget>
  <widget class_="button" type_="set" text_="Export"
   value_="@r" newvalue_="{@r+1}"/>
</dynamic>

Example: Rendering to various targets

The following example demonstrates how a QuickApp specified within a nest widget can be rendered to different targets using the target_ attribute. In this example, a dropdown widget is provided so that the user can select which render target to use. Once the user clicks the Render button, the nest widget is triggered to update and uses the value saved to the targ dynamic variable as the value for the target_ attribute. Based on which target is specified, the appropriate attributes specified within the <render> tag for the nested QuickApp are applied, and the QuickApp is rendered to the target.

<dynamic targ="">
  <widget class_="dropdown" value_="@targ" 
   label_="Choose render target">
    <table>pdf;xlsx;data;web
    </table>
  </widget>
  <widget class_="button" type_="submit" text_="Render" submit_="dl"/>
  <widget class_="nest" name="dl" update_="manual" invmode_="hide" 
   require_="@targ" target_="{@targ}">
    <dynamic store="1,2,3">
      <render>
        <web into_="browsertab">
          <widget class_="grid" 
           headerbgcolor_="blue" headerfontcolor_="yellow"/>
        </web>
        <xlsx headerbgcolor_="green" headerfontcolor_="white"/>
        <data headers_="names,labels" filename_="datadump" ext_="txt"/>
      </render>
      <widget class_="dropdownlist" value_="@store" 
       base_="pub.demo.retail.item" label_="Select a store">
        <tabu breaks="store"/>
      </widget>
      <widget class_="grid" base_="pub.demo.retail.item" 
       require_="{@store<>''}" invmode_="hide">
        <sel value="store={@store}"/>
      </widget>
    </dynamic>
  </widget>
</dynamic>

For instance, if the user selects xlsx from the dropdown widget and clicks Render, the nested QuickApp is rendered to an Excel workbook, and the header of the grid widget in the nested QuickApp renders as white text on a green background.

If the user selects web from the dropdown widget and clicks Render, the nested QuickApp is rendered to a new browser tab. The header of the grid widget in the nested QuickApp renders as yellow text on a blue background, since the headerbgcolor_ and headerfontcolor_ are specified to the grid widget inside the <web> tag. Those attributes are applied to all grid widgets when rendered to a web target.

Note that the dropdownlist widget in the nested QuickApp is rendered in the web target, but not when rendered to Excel, PDF, or a data target

Using <switch> inside of class_="nest"

Note that the variable j referenced inside <switch> is defined outside the inner <dynamic>.

<dynamic j="0">
  <widget class_="nest">
    <dynamic i="0">
      <switch>
        <case when="{@j=1}">
          <widget class_="text" text_="hello"/>
        </case>
        <else>
          <widget class_="text" text_="goodbye"/>
        </else>
        </switch>
      </dynamic>
    </widget>
  </dynamic>