I've Never Had A Good Story For View-Rendering Helpers In ColdFusion

snippet-1.cfm

<button
	data-action="parent##logAction"
	data-parent-child-id-param="#encodeForHtmlAttribute( item.id )#"
	data-parent-child-data-param="#encodeForHtmlAttribute( serializeJson( item ) )#">
	Trigger Parent Action
</button>

test.cfm

<cfscript>

	// In a production app, this ColdFusion component would be cached in the application
	// scope, or wired into a dependency-injection mechanism.
	application.viewHelper = new ViewHelper();

	// Then, I would likely alias it for the sake of brevity wherever it was needed.
	view = application.viewHelper;

</cfscript>
<cfoutput>

	<!--- Serializing complex values (as JSON) for use in an attribute. --->
	<form>
		<input
			type="hidden"
			name="state"
			#view.attr( "value", { id: 1, name: "Ben" } )#
		/>
	</form>

	<!--- Optionally including [selected] attribute based on condition. --->
	<form>
		<select>
			<cfloop index="i" from="1" to="10">
				<option
					#view.attr( "value", i )#
					#view.selectedAttr( i == 5 )#>
					#i#
				</option>
			</cfloop>
		</select>
	</form>

	<!--- Optionally including [disabled] attribute based on condition. --->
	<form>
		<button #view.disabledAttr( false )#>
			I am enabled
		</button>
		<button #view.disabledAttr( true )#>
			I am disabled
		</button>
	</form>

	<!--- Optionally including [checked] attribute based on condition. --->
	<form>
		<cfloop index="i" from="1" to="5">
			<input
				type="radio"
				name="r"
				value="1"
				#view.checkedAttr( i == 2 )#
			/>
		</cfloop>	
	</form>

	<!--- Coalescing [class] attribute based on conditions. --->
	<p #view.classAttr([
		"block": true,
		"block--modifier": true,
		"block__element": false
		])#>
		I have CSS classes.
	</p>

	<!--- Coalescing [style] attribute. --->
	<p #view.styleAttr([
		"color": "red",
		"font-style": "italic"
		])#>
		I have styles.
	</p>

	<!--- I render multiple "data-" attributes with encoded values. --->
	<p #view.dataAttrs([
		"action": "parent##logAction",
		"parent-child-id-param": 1,
		"parent-child-data-param": { id: 1, name: "Ben Nadel" }
		])#>
		I have "data-"" attributes.
	</p>

</cfoutput>

ViewHelper.cfc

component
	output = false
	hint = "I provide utility methods for rendering HTML in a view template."
	{

	/**
	* I output the given attribute with proper attribute encoding. If the value is a
	* complex data structure, it is serialized as JSON.
	*/
	public string function attr(
		required string name,
		any value = ""
		) {

		if ( isSimpleValue( value ) ) {

			return( "#name#=""#encodeForHtmlAttribute( value )#""" );

		} else {

			return( "#name#=""#encodeForHtmlAttribute( serializeJson( value ) )#""" );

		}

	}


	/**
	* I output the given boolean attribute if the given condition is Truthy.
	*/
	public string function booleanAttr(
		required string name,
		any condition = false
		) {

		return( isTruthy( condition ) ? name : "" );

	}


	/**
	* I output the "checked" boolean attribute if the given condition is Truthy.
	*/
	public string function checkedAttr( any condition = false ) {

		return( booleanAttr( "checked", condition ) );

	}


	/**
	* I output the "class" attribute, including every key in the given collection whose
	* corresponding value is Truthy.
	*/
	public string function classAttr( required struct values ) {

		var classNames = filterStructOnTruthyValues( values )
			.keyArray()
			.toList( " " )
		;

		if ( classNames.len() ) {

			return( "class=""#classNames#""" );

		}

		return( "" );

	}


	/**
	* I output a "data-*" attribute for each key-value pair in the given collection.
	*/
	public string function dataAttrs( required struct values ) {

		var pairs = values.keyArray()
			.map(
				( key ) => {

					return( attr( "data-#key#", values[ key ] ) );

				}
			)
			.toList( " " )
		;

		return( pairs );

	}


	/**
	* I output the "disabled" boolean attribute if the given condition is Truthy.
	*/
	public string function disabledAttr( any condition = false ) {

		return( booleanAttr( "disabled", condition ) );

	}


	/**
	* I output the "selected" boolean attribute if the given condition is Truthy.
	*/
	public string function selectedAttr( any condition = false ) {

		return( booleanAttr( "selected", condition ) );

	}


	/**
	* I output the "style" attribute using the given key-value CSS properties.
	*/
	public string function styleAttr( required struct values ) {

		var pairs = [];

		for ( var key in values ) {

			pairs.append( "#key#: #values[ key ]# ;" );

		}

		var styles = pairs.toList( " " );

		if ( styles.len() ) {

			return( "style=""#styles#""" );

		}

		return( "" );

	}

	// ---
	// PRIVATE METHODS.
	// ---

	/**
	* I filter the given collection down to the keys with Turthy values.
	*/
	private struct function filterStructOnTruthyValues( required struct collection ) {

		var filteredCollection = collection.filter(
			( key, value ) => {

				// CAUTION: The filter() method will include null keys in the iteration.
				// As such, we can't use the isTruthy() method on its own or we'll run
				// into null reference errors.
				return( ! isNull( value ) && isTruthy( value ) );

			}
		);

		return( filteredCollection );

	}


	/**
	* I determine if the given value is a Falsy.
	*/
	private boolean function isFalsy( any value = false ) {

		if ( ! isSimpleValue( value ) ) {

			return( false );

		}

		if ( isBoolean( value ) || isNumeric( value ) ) {

			return( ! value );

		}

		return( value == "" );

	}


	/**
	* I determine if the given value is a Truthy (which is any value that isn't Falsy).
	*/
	private boolean function isTruthy( any value = false ) {

		return( ! isFalsy( value ) );

	}

}