When compiling, generates compiled bytecode for a class with the given package-qualified :name (which, as all names in these parameters, can be a string or symbol), and writes the .class file to the *compile-path* directory. When not compiling, does nothing. The gen-class construct contains no implementation, as the implementation will be dynamically sought by the generated class in functions in an implementing Clojure namespace. Given a generated class org.mydomain.MyClass with a method named mymethod, gen-class will generate an implementation that looks for a function named by (str prefix mymethod) (default prefix: "-") in a Clojure namespace specified by :impl-ns (defaults to the current namespace). All inherited methods, generated methods, and init and main functions (see :methods, :init, and :main below) will be found similarly prefixed. By default, the static initializer for the generated class will attempt to load the Clojure support code for the class as a resource from the classpath, e.g. in the example case, ``org/mydomain/MyClass__init.class``. This behavior can be controlled by :load-impl-ns Note that methods with a maximum of 18 parameters are supported. In all subsequent sections taking types, the primitive types can be referred to by their Java names (int, float etc), and classes in the java.lang package can be used without a package qualifier. All other classes must be fully qualified. Options should be a set of key/value pairs, all except for :name are optional: :name aname The package-qualified name of the class to be generated :extends aclass Specifies the superclass, the non-private methods of which will be overridden by the class. If not provided, defaults to Object. :implements [interface ...] One or more interfaces, the methods of which will be implemented by the class. :init name If supplied, names a function that will be called with the arguments to the constructor. Must return [ [superclass-constructor-args] state] If not supplied, the constructor args are passed directly to the superclass constructor and the state will be nil :constructors {[param-types] [super-param-types], ...} By default, constructors are created for the generated class which match the signature(s) of the constructors for the superclass. This parameter may be used to explicitly specify constructors, each entry providing a mapping from a constructor signature to a superclass constructor signature. When you supply this, you must supply an :init specifier. :post-init name If supplied, names a function that will be called with the object as the first argument, followed by the arguments to the constructor. It will be called every time an object of this class is created, immediately after all the inherited constructors have completed. Its return value is ignored. :methods [ [name [param-types] return-type], ...] The generated class automatically defines all of the non-private methods of its superclasses/interfaces. This parameter can be used to specify the signatures of additional methods of the generated class. Static methods can be specified with ^{:static true} in the signature's metadata. Do not repeat superclass/interface signatures here. :main boolean If supplied and true, a static public main function will be generated. It will pass each string of the String[] argument as a separate argument to a function called (str prefix main). :factory name If supplied, a (set of) public static factory function(s) will be created with the given name, and the same signature(s) as the constructor(s). :state name If supplied, a public final instance field with the given name will be created. You must supply an :init function in order to provide a value for the state. Note that, though final, the state can be a ref or agent, supporting the creation of Java objects with transactional or asynchronous mutation semantics. :exposes {protected-field-name {:get name :set name}, ...} Since the implementations of the methods of the generated class occur in Clojure functions, they have no access to the inherited protected fields of the superclass. This parameter can be used to generate public getter/setter methods exposing the protected field(s) for use in the implementation. :exposes-methods {super-method-name exposed-name, ...} It is sometimes necessary to call the superclass' implementation of an overridden method. Those methods may be exposed and referred in the new method implementation by a local name. :prefix string Default: "-" Methods called e.g. Foo will be looked up in vars called prefixFoo in the implementing ns. :impl-ns name Default: the name of the current ns. Implementations of methods will be looked up in this namespace. :load-impl-ns boolean Default: true. Causes the static initializer for the generated class to reference the load code for the implementing namespace. Should be true when implementing-ns is the default, false if you intend to load the code via some other method.