Previous: Operations, Up: The object model of ASDF [Contents][Index]
A component represents a source file or
(recursively) a collection of components.
A system is (roughly speaking) a top-level component
that can be found via find-system
.
A system designator is a string or symbol and behaves just like any other component name (including with regard to the case conversion rules for component names).
Given a system designator, find-system
finds and returns a system.
If no system is found, an error of type
missing-component
is thrown,
or nil
is returned if error-p
is false.
To find and update systems, find-system
funcalls each element
in the *system-definition-search-functions*
list,
expecting a pathname to be returned.
The resulting pathname is loaded if either of the following conditions is true:
last-modified
time exceeds the last-modified
time
of the system in memory
When system definitions are loaded from .asd files,
a new scratch package is created for them to load into,
so that different systems do not overwrite each others operations.
The user may also wish to (and is recommended to)
include defpackage
and in-package
forms
in his system definition files, however,
so that they can be loaded manually if need be.
The default value of *system-definition-search-functions*
is a list of two functions.
The first function looks in each of the directories given
by evaluating members of *central-registry*
for a file whose name is the name of the system and whose type is asd.
The first such file is returned,
whether or not it turns out to actually define the appropriate system.
The second function does something similar,
for the directories specified in the source-registry
.
Hence, it is strongly advised to define a system
foo in the corresponding file foo.asd.
• Common attributes of components: | ||
• Pre-defined subclasses of component: | ||
• Creating new component types: |
Previous: Operations, Up: The object model of ASDF [Contents][Index]