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Defense > Developing with design tools > Using the Symbol Editor > Using more features of the Symbol Editor > Using expressions
 
Using expressions
Expressions are used to customize the format and value of a parameter. For example, you can use an expression to do the following to an object:
*Blink in two different colors
*Display the date in a specific format
*Join the value of two expressions
*Return the square root of a parameter
An expression can be set on any attribute contained in a symbol.
To use an expression on an object:
1. Open the symbol you made in Creating a rotation interactor for multiple objects.
2. Select the Text object.
3. Click the Text tab in the Styling Customizer.
4. Right-click the Label field.
A pop-up menu appears.
5. Click Enter an Expression.
6. Delete the contents of the Label field.
It is changed into a drop down list.
7. Click the down arrow on the right of the Label field.
The list of expressions appears.
8. Select the @rotationValue expression.
9. Enter the expression as follows: rotationValue(0,360,@rotate,0,360).
10. Test this symbol by clicking the Preview button.
As you rotate the mouse over the symbol, the Text label is updated to show the angle of rotation.
Expressions can combine other expressions, model attributes and string literals. For example, the following expression prints the integer value of a parameter in a string.
concat("the rotation value is ", rotationValue(0,360,@rotate,0,360), ".")
NOTE When creating expressions, always select values from the list, do not type the parameter name or expression by hand.
Possible expressions are listed in the following table.
Symbol Editor expressions
Name
Description
Example
parameter specification
Any parameter in the symbol.
@myparam
parameter (parametername)
Any parameter in the symbol specified as a String.
@parameter("myparam")
int(expr)
Evaluates the argument as an expression. The result is a number of type Integer.
int(@param*100)
long(expr)
Evaluates the argument as an expression. The result is a number of type Long.
long(@x+@y)
float(expr)
Evaluates the argument as an expression. The result is a number of type Float.
float(cos(@value))
double(expr)
Evaluates the argument as an expression. The result is a number of type Double.
double(@value*3)
cast(expr,type)
Casts a value to a type. The second argument can be a fully qualified class name (entered as a String ) or a class object.
cast(@param,"java.awt.Color")
min(arg0, arg1, ...)
Returns the smallest number among the arguments. All arguments must be numbers. Unless otherwise specified, the arguments are interpreted as numbers of type Double.
min(@x,@y,0)
max(arg0, arg1, ...)
Returns the largest number among the arguments. All arguments must be numbers. Unless otherwise specified, the arguments are interpreted as numbers of type Double.
max(@x,@y,1000)
invoke(obj,methodname,signature,arg...)
Invokes a method on the object by introspection. The signature string specifies the argument types of the method as a comma separated list of (fully qualified) type names. The object and the arguments must be cast accordingly.
The specification @|invoke(cast(@val,java.lang.String), substring,"int,int",int(3),int(6)). This use corresponds to the call ((String)@val).substring(3,6).
invokeStatic(classname,methodname,signature,arg...)
Invokes a static method on the specified class by introspection. The signature string specifies the argument types of the method as a comma separated list of (fully qualified) type names. The arguments must be cast accordingly.
The specification @|invokeStatic("java.lang.Math", "atan2","double,double",double(0.6), double(0.4)). This use corresponds to the call java.lang.Math.atan2(0.6,0.4).
new(classname,signature,arg...)
Invokes a constructor on the specified class by introspection. The signature string specifies the argument types of the method as a comma separated list of (fully qualified) type names. The arguments must be cast accordingly.
The specification @|new("java.util.Date","long", long(1293840000000)). This use corresponds to the call java.util.Date(1293840000000L).
abs(arg)
Absolute value of the parameter.
sin(arg)
Returns the trigonometric sine of an angle.
cos(arg)
Returns the trigonometric cosine of an angle.
tan(arg)
Returns the trigonometric tangent of an angle.
asin(arg)
Returns the arc sine of an angle, in the range of -pi/2 through pi/2.
acos(arg)
Returns the arc cosine of an angle, in the range of 0.0 through pi.
atan(arg)
Returns the arc tangent of an angle, in the range of -pi/2 through pi/2.
log(exp)
Returns the natural logarithm (base e) of a double value
exp(arg)
Returns Euler's number e raised to the power of a double value.
ceil(arg)
Returns the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer.
floor(arg)
Returns the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer.
rint(arg)
Returns the double value that is closest in value to the argument and is equal to a mathematical integer.
round(arg)
Returns the integer value that is closest to the argument. The result is rounded to an integer by adding 1/2, then taking the floor of the result
sqrt(arg)
Returns the correctly rounded positive square root of a double value.
rotationValue(min,max,value,start,end)
Calculates the rotation angle by mapping the value parameter from range 0 to max - min to the range start to end.
rotationValue(0,100,@rotate,10,20)
random()
Returns a random number between 0 and 1.
random()
random(n)
Returns a random number between 0 and n.
random(16)
point(x, y)
Returns a point of type IlvPoint.
point(5,5)
rect(x, y, w, h)
Returns a rectangle of type IlvRect.
rect(0,0,100,50)
blinkingColor(onColor, offColor)
Returns an alternating blinking color with the timing specified in the IlvBlinkingRenderer.
blinking(green,yellow)
blinkingColor(onColor, offColor, onTime, offTime)
Returns an alternating blinking color with the timing, onTime and offTime, specified in milliseconds.
blinking(green,yellow,500,1000)
brighterColor(color)
Returns a color that corresponds to Color.brighter.
brighterColor(gray)
darkerColor(color)
Returns a color that corresponds to Color.darker.
darkerColor(red)
concat(arg1,...,argn)
Returns the concatenation of the arguments arg1,...,argn as strings.
concat("result is: ",@result)
emptyString()
Returns an empty string.
emptyString()
messageFormat(format,arg0,arg1,...)
Formats different strings to a specific message format. See java.text.MessageFormat for details.
messageFormat('{0}: {1,number,#.##}','result',44.2874).
This use returns 44.28"
decimalFormat(format,arg)
Returns a formatted string from a number. See java.text.DecimalFormat for details.
decimalFormat("#.#", pi)
This returns "3.1".
simpleDateFormat(format, arg[, locale])
Returns a formatted string from a date. See java.text.SimpleDateFormat for details.
simpleDateFormat("MM/dd/yyyy",@date)
This returns "10/01/2001"
customFormat(formatBean,arg0,arg1,...)
Returns a formatted string. The formatBean parameter must be a Java object of type MessageFormat, NumberFormat, or DateFormat, typically defined using the @#id syntax.
customFormat(@#format, '{0} {1}', 'result', 44.2874)
locale()
Returns the locale of the object being styled or of the current context.
locale()
localized(resourceBundleName, resourceName[, locale])
Returns the localized value of the designated resource, fetched from a ResourceBundle, as a string.
localized('ilog.views.messages','ilog.views.defaultLabel')
childrenCount()
Returns the number of children.
childrenCount()==0
Many of these expressions are CSS functions, see Using custom functions. If you want to register your own predefined CSS functions in the Symbol Editor, extract the file ilog/views/util/css/cssfunctions.properties from jviews-framework-all.jar. This file contains the settings for predefined CSS functions. Follow the instructions in this file to add your own CSS functions.
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