Adobe 38043740 Developing Applications - Page 868

DEVELOPING COLDFUSION 9 APPLICATIONS 863 Requesting and Presenting Information Note: You can bind to the display text of a select box, instead of the value, by specifying an attribute name of innerHTML. Note: When you bind to a check box, use the @click event specifier to ensure that the bind expression is triggered in Internet Explorer when the user selects or deselects the check box, not when the box loses focus. Grids and trees do not have default bind attributes. • Always specify a grid target attribute by using the format {gridID.columnName}. The bind expression gets the value of the specified column in the selected row. • For trees, you must bind to a specific node in the tree. Specify the node by using the node ID or an explicit path to the node. To bind to a Spry data set element or attribute, use standard Spry path notation. For example, specify an element name. The event value By default, the bind expression function executes each time the control specified in the bind parameter has an onChange event. To trigger updates on a different JavaScript event, end the bind expression with an at sign (@) and the event name, without the "on" prefix. The following code, for example, executes the getChoices CFC each time the user presses the mouse button while the pointer is over the book control: bind="cfc:myapp.bookorder.getChoices({inputForm:book@mousedown})" Note: To bind to a cfinput control with type attribute of button, specify a bind event setting, such as click. The change event is the default event has no effect. When you bind to a Spry data set, do not specify an event. The expression is evaluated when the selected row changes in the data set, or when the data set reloads with new data. You can also specify that a specific bind parameter never triggers bind expression reevaluation, by specifying @none as the event. This is useful, for example, if a bind expression uses multiple bind parameters binding to different form fields, and you want the bind expression to trigger changes only when one of the fields changes, not when the others change. In this case, you would specify @none for the remaining fields, so events from those fields would not trigger the bind. The following code shows this use: bind="cfc:books.getinfo({iForm:book}, {iForm:author@none})" The @none event specifier is also useful when used with autosuggest text inputs, trees and grids, as follows: • When you use an autosuggest text input, the bind expression is evaluated as a user types in text, and picks up data from all bind parameters, including those parameters with @none specified. Therefore, for autosuggest, specify @none for all bind parameters, because there is no way for it to react to changes in the parameters. • When you call the ColdFusion.Grid.refresh or ColdFusion.Tree.refresh function, the function fetches data from all bind parameters when it evaluates the bind expression, including any parameters with @none specified. If you specify @none for all bind parameters, the tree or grid might not respond to changes in other controls, but gets data from all the bind parameters each time you explicitly refresh it. Using CFC functions in bind expressions As with JavaScript functions, you pass arguments to a CFC function specified in a bind expression positionally. When you do this, the argument names in a CFC function definition do not have to be the same as the bind parameter names, but the arguments in the bind expression must be in the same order as the arguments in the CFC function definition. Alternatively, you pass named CFC function arguments. Then, the bind expression and CFC function must use the same names for the arguments, and the function does not have to define the arguments in the same order as they are passed. To specify argument names in a bind expression, use a format such as the following, which uses two named parameters, arg1 and arg2: Last updated 1/20/2012