# 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:
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:
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:
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