Variables and Functions in Java

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Variables and Functions
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As you have just seen, the FXType and FXValue classes represent, respectively, the types and values of variables and functions in the JavaFX Reflection APITo make use of them, you need to get a reference to a real variable or function Variables and functions are members of JavaFX classesThis applies even to those variables and functions that appear outside of a class definition, which are actually members of the script class (that is, the class whose name is the same as that of the script)A class member is represented by the class FXMember, which has subclasses FXVarMember, which represents a member variable, and FXFunctionMember, which represents a member function, as shown in Figure 13-4
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FXMember
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FXVarMember
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FXFunctionMember
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Figure 13-4
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FXMember and its subclasses
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The FXMember class has three methods, listed in Table 13-4, that return information common to both variable and function members
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Variables and Functions
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Table 13-4 Method
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Methods of the FXMember Class Description
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Returns the FXClassType object for the class that owns this member Returns the variable or function name Returns true for a script variable (which is implemented as a static member of a Java class), false for a script variable
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public FXClassType getDeclaringClass() public String getName() public Boolean isStatic()
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In the sections that follow, we ll use the code in Listing 13-1 to illustrate how to discover the variables and functions of a class
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Listing 13-1
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
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Reflection Example
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package javafxreflection; public var scriptVar = "A script variable"; public function add(arg1:Integer, arg2:Integer):Integer { arg1 + arg2 } public var aFunction = add; public class FunctionsAndVariables { public var instanceVar = 0; public function multiply(arg1:Number, arg2:Number):Number { arg1 * arg2 } public function multiply(arg1:Integer, arg2:Integer):Integer { arg1 * arg2; } public function sayHello():Void { println("Hello"); } public function say(what:String):Void { println(what); } }
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This code is in a file called javafxreflection/FunctionsAndVariablesfx in the JavaFX Book Desktop project Notice that it contains a script variable called scriptVar,
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13 Reflection
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a declaration of a function called add(), a function variable called aFunction, and a declaration of a class called FunctionsAndVariablesWe ll make use of all these elements in the sections that follow
Reflecting on Variables
Reflective access to a variable is provided by the FXVarMember classTo discover the variables of a class, you first need to get its FXClassType object, which, as you have already seen, is obtained from the FXContext:
var ctx = FXContextgetInstance(); var classType = ctxfindClass("javafxreflectionFunctionsAndVariables");
After you have the FXClassType object for a class, you can use it to get reflective information for a specific variable of that class or for all of its variables Getting a Named Variable The getVariable() method of FXClassType returns the FXVarMember object for a named variable of that classThe following code gets the FXVarMember object for the script variable called scriptVar, declared on line 3 of Listing 13-1:
var scriptVarMember = classTypegetVariable("scriptVar"); println("scriptVar name: {scriptVarMembergetName()}"); println(" script variable {scriptVarMemberisStatic()}");
The output from this code is as follows:
scriptVar name: scriptVar script variable True
You can get the FXVarMember object for the instance variable instanceVar declared on line of Listing 13-1 in exactly the same way:
var instanceVarMember = classTypegetVariable("instanceVar"); println("instanceVar name: {instanceVarMembergetName()}"); println(" script variable {instanceVarMemberisStatic()}");
This code produces the following result:
instanceVar name: instanceVar script variable false
In both of these examples, the variable is declared by the actual class whose object is being usedThe getVariable() method will also return information for variables that are declared in any of the superclasses of that class If the getVariable() function is invoked with the name of a variable that is not declared in the target class or any of its subclasses, it returns null
FXClassType
Variables and Functions
The FXVarMember class provides functions that allow you get and set the value of the variable (see the section Reading and Setting Variable Values ), and the method getType() that returns the type of the variable as an FXType object Here s how you get and print the declared type of the variable instanceVar:
println("instanceVar type: {instanceVarMembergetType()getName()}");
This code prints the following: