BlitzMax/Modules/BASIC/Reflection

BlitzMax provides limited support for a form of runtime reflection.

Using reflection, programs can 'inspect' objects and types at runtime. You can determine the fields and methods contained in an object or type, set and get object fields and invoke - or 'call' - object methods.

To use reflection, you first need a TTypeId object. TTypeId objects correspond to BlitzMax user defined types, and there is a single TTypeId object for every user defined type in the program. There are also TTypeId objects for the 'primitive' types - byte, short, int, long, float, double and string. TTypeId objects are returned by the TTypeId.ForName and TTypeId.ForObject functions.

Once you have a TTypeId object, you can inspect the fields and methods of a user defined type using the EnumFields and EnumMethods methods. These methods return TField and TMethod objects that describe the fields and methods within the type. For example: Strict

Type TMyType Field x,y,z End Type

Local id:TTypeId=TTypeId.ForName( "TMyType" )

For Local fld:TField=EachIn id.EnumFields Print fld.Name+":"+fld.TypeId.Name Next This simple program will print "x:Int", "y:Int" and "z:Int" - the names and types of the fields within TMyType. Note that this is done without actually creating a new TMyType.

The following example sets the fields of an object: Strict

Type TMyType Field x,y,z End Type

Local obj:TMyType=New TMyType Local id:TTypeId=TTypeId.ForObject( obj )

For Local fld:TField=EachIn id.EnumFields fld.Set obj,String( Rand(10) ) Next

Print obj.x+","+obj.y+","+obj.z In this case we need an actual instance of TMyType, otherwise we have nothing to set the fields of! Also, we have used TTypeId.ForObject instead of TTypeId.ForName to get a TTypeId. While in this case TTypeId.ForName could have been used to achieve the same result, in general we may not know the exact type of the object, and therefore we wont know its type name.

Also note that the code that actually sets the fields uses String( Rand(10) ). This is because the Set method takes an object - but our fields are ints! BlitzMax reflection deals with this by using strings to represent numeric types. The same rule applies to the Get method. Any numeric fields will be returned as strings which you must then convert to the appropriate type if necessary.

Finally, let's invoke an object method: Strict

Type TMyType Method Update( t# ) Print "TMyType.Update:"+t End Method End Type

Local obj:TMyType=New TMyType Local id:TTypeId=TTypeId.ForObject( obj )

Local update:TMethod=id.FindMethod( "Update" )

update.Invoke obj,[String( .25 )] This example uses FindMethod to locate a type method and Invoke to call it. Arguments to the method are contained in an object array, and again the float argument is converted to a string.

In addition to the TTypeId, TField and TMethod types, the BlitzMax reflection module also declares a number of global TTypeId objects:


 * ByteTypeId 
 * ShortTypeId 
 * IntTypeId 
 * LongTypeId 
 * FloatTypeId 
 * DoubleTypeId 
 * StringTypeId 
 * ObjectTypeId 

These may be used instead of the corresponding TTypeId.ForName call. For example, TTypeId.ForName( "Int" ) and IntTypeId will return the same object.

=Globals=

ByteTypeId
Global ByteTypeId:TTypeId=New TTypeId.Init( "Byte",1 )

Description: Primitive byte type

ShortTypeId
Global ShortTypeId:TTypeId=New TTypeId.Init( "Short",2 )

Description: Primitive short type

IntTypeId
Global IntTypeId:TTypeId=New TTypeId.Init( "Int",4 )

Description: Primitive int type

LongTypeId
Global LongTypeId:TTypeId=New TTypeId.Init( "Long",8 )

Description: Primitive long type

FloatTypeId
Global FloatTypeId:TTypeId=New TTypeId.Init( "Float",4 )

Description: Primitive float type

DoubleTypeId
Global DoubleTypeId:TTypeId=New TTypeId.Init( "Double",8 )

Description: Primitive double type

StringTypeId
Global StringTypeId:TTypeId=New TTypeId.Init( "String",4,bbRefStringClass )

Description: Primitive string type

ObjectTypeId
Global ObjectTypeId:TTypeId=New TTypeId.Init( "Object",4,bbRefObjectClass )

Description: Primitive object type

ArrayTypeId
Global ArrayTypeId:TTypeId=New TTypeId.Init( "Null[]",4,bbRefArrayClass )

Description: Primitive array type

=Types=

TMember
Type member - field or method.


 * Name
 * TypeId
 * MetaData

TMember: Methods
Method Name$

Description: Get member name

Method TypeId:TTypeId

Description: Get member type

Method MetaData$( key$="" )

Description: Get member meta data

TField
Type field


 * Get
 * GetInt
 * GetLong
 * GetFloat
 * GetDouble
 * GetString
 * Set
 * SetInt
 * SetLong
 * SetFloat
 * SetDouble
 * SetString

TField: Methods
Method Get:Object( obj:Object )

Description: Get field value

Method GetInt:Int( obj:Object )

Description: Get int field value

Method GetLong:Long( obj:Object )

Description: Get long field value

Method GetFloat:Float( obj:Object )

Description: Get float field value

Method GetDouble:Double( obj:Object )

Description: Get double field value

Method GetString$( obj:Object )

Description: Get string field value

Method Set( obj:Object,value:Object )

Description: Set field value

Method SetInt( obj:Object,value:Int )

Description: Set int field value

Method SetLong( obj:Object,value:Long )

Description: Set long field value

Method SetFloat( obj:Object,value:Float )

Description: Set float field value

Method SetDouble( obj:Object,value:Double )

Description: Set double field value

Method SetString( obj:Object,value$ )

Description: Set string field value

TMethod
Type method


 * ArgTypes
 * Invoke

TMethod: Methods
Method ArgTypes:TTypeId[]

Description: Get method arg types

Method Invoke:Object( obj:Object,args:Object[] )

Description: Invoke method

TTypeId
Type id


 * Name
 * MetaData
 * SuperType
 * ArrayType
 * ElementType
 * ExtendsType
 * DerivedTypes
 * NewObject
 * Fields
 * Methods
 * FindField
 * FindMethod
 * EnumFields
 * EnumMethods
 * NewArray
 * ArrayLength
 * ArrayDimensions
 * GetArrayElement
 * SetArrayElement


 * ForName
 * ForObject
 * EnumTypes

TTypeId: Methods
Method Name$

Description: Get name of type

Method MetaData$( key$="" )

Description: Get type meta data

Method SuperType:TTypeId

Description: Get super type

Method ArrayType:TTypeId(dims:Int = 1)

Description: Get array type

Method ElementType:TTypeId

Description: Get element type

Method ExtendsType( typeId:TTypeId )

Description: Determine if type extends a type

Method DerivedTypes:TList

Description: Get list of derived types

Method NewObject:Object

Description: Create a new object

Method Fields:TList

Description: Get list of fields

Information: Only returns fields declared in this type, not in super types.

Method Methods:TList

Description: Get list of methods

Information: Only returns methods declared in this type, not in super types.

Method FindField:TField( name$ )

Description: Find a field by name

Information: Searchs type hierarchy for field called name.

Method FindMethod:TMethod( name$ )

Description: Find a method by name

Information: Searchs type hierarchy for method called name.

Method EnumFields:TList( list:TList=Null )

Description: Enumerate all fields

Information: Returns a list of all fields in type hierarchy

Method EnumMethods:TList( list:TList=Null )

Description: Enumerate all methods

Information: Returns a list of all methods in type hierarchy - TO DO: handle overrides!

Method NewArray:Object( length, dims:Int[] = Null )

Description: Create a new array

Method ArrayLength( array:Object, dim:Int = 0 )

Description: Get array length

Method ArrayDimensions:Int( array:Object )

Description: Get the number of dimensions

Method GetArrayElement:Object( array:Object,index )

Description: Get an array element

Method SetArrayElement( array:Object,index,value:Object )

Description: Set an array element

TTypeId: Functions
Function ForName:TTypeId( name$ )

Description: Get Type by name

Function ForObject:TTypeId( obj:Object )

Description: Get Type by object

Function EnumTypes:TList

Description: Get list of all types