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=Reflection as Language Feature vs Reflection as Package= | =Reflection as Language Feature vs Reflection as Package= | ||
For the sake of simplicity, we take Ruby and Java to represent languages that have Reflection as a language feature and reflection as a package respectively. | For the sake of simplicity, we take Ruby and Java to represent languages that have Reflection as a language feature and reflection as a package respectively.<br /> | ||
One of the languages that has reflection as a built-in language feature is Ruby. Objects in Ruby support reflection by default, hence it is not necessary to use any external or additional libraries. In essence, the programmer does not need to do anything special to start using reflection, it is a native part of the language. Additionally, Ruby's intuitive syntax and ease of use make it possible for someone who is not an expert to write Ruby code that uses reflection. | One of the languages that has reflection as a built-in language feature is Ruby. Objects in Ruby support reflection by default, hence it is not necessary to use any external or additional libraries. In essence, the programmer does not need to do anything special to start using reflection, it is a native part of the language. Additionally, Ruby's intuitive syntax and ease of use make it possible for someone who is not an expert to write Ruby code that uses reflection.<br /> | ||
Reflection in Java is achieved by making method calls on a Class object. Before using reflection on an object, first it is necessary to map it to an instance of Class. It is important to note that this method only works for types that are derived from Object, not all types in Java are an object, e.g. boolean. | Reflection in Java is achieved by making method calls on a Class object. Before using reflection on an object, first it is necessary to map it to an instance of Class. It is important to note that this method only works for types that are derived from Object, not all types in Java are an object, e.g. boolean. | ||
=Reflection as Package= | =Reflection as Package= | ||
Revision as of 03:25, 8 September 2010
Introduction to Reflection
Reflection is a language feature that enables a program to examine itself at runtime and possibly change its behavior accordingly. It was introduced by Brian Cantwell Smith as a framework for language extension.There are two aspects to reflection :
- Introspection - the ability for a program to observe and reason about its own state.
- Intercession - the ability for a program to modify its own execution state or alter its own interpretation or meaning.
What is crucial here is that a given program can behave not only as a function, but also as a data structure that can be examined and manipulated to change its behavior. These properties lead to an easily extensible language since the structures used by the language implementation are accessible to the programmer. The programmer can now define programming constructs that would otherwise have been either impossible or extremely difficult to define. These properties have led to the adoption of reflection as a primary means for language extensibility. Reflection is most commonly used in many dynamically typed languages such as Ruby,Smalltalk, Objective-c and scripting languages like Perl,PHP. Statically typed languages such as Java, ML or Haskell also support reflection. Reflective programming languages and platforms provides a comprehensive list of all languages and platforms supporting reflection.
Reflection as Language Feature vs Reflection as Package
For the sake of simplicity, we take Ruby and Java to represent languages that have Reflection as a language feature and reflection as a package respectively.
One of the languages that has reflection as a built-in language feature is Ruby. Objects in Ruby support reflection by default, hence it is not necessary to use any external or additional libraries. In essence, the programmer does not need to do anything special to start using reflection, it is a native part of the language. Additionally, Ruby's intuitive syntax and ease of use make it possible for someone who is not an expert to write Ruby code that uses reflection.
Reflection in Java is achieved by making method calls on a Class object. Before using reflection on an object, first it is necessary to map it to an instance of Class. It is important to note that this method only works for types that are derived from Object, not all types in Java are an object, e.g. boolean.