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Diffstat (limited to 'doc/define.n')
| -rw-r--r-- | doc/define.n | 175 |
1 files changed, 169 insertions, 6 deletions
diff --git a/doc/define.n b/doc/define.n index b489e5f..883d5fa 100644 --- a/doc/define.n +++ b/doc/define.n @@ -1,5 +1,5 @@ '\" -'\" Copyright (c) 2007 Donal K. Fellows +'\" Copyright (c) 2007-2018 Donal K. Fellows '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. @@ -39,6 +39,27 @@ used as the \fIdefScript\fR argument. The following commands are supported in the \fIdefScript\fR for \fBoo::define\fR, each of which may also be used in the \fIsubcommand\fR form: .TP +\fBclassmethod\fI name\fR ?\fIargList bodyScrip\fR? +.VS TIP478 +This creates a class method, or (if \fIargList\fR and \fIbodyScript\fR are +omitted) promotes an existing method on the class object to be a class +method. The \fIname\fR, \fIargList\fR and \fIbodyScript\fR arguments are as in +the \fBmethod\fR definition, below. +.RS +.PP +Class methods can be called on either the class itself or on the instances of +that class. When they are called, the current object (see the \fBself\R and +\fBmy\fR commands) is the class on which they are called or the class of the +instance on which they are called, depending on whether they are called on the +class or an instance of the class, respectively. If called on a subclass or +instance of the subclass, the current object is the subclass. +.PP +In a private definition context, the methods as invoked on classes are +\fInot\fR private, but the methods as invoked on instances of classes are +private. +.RE +.VE TIP478 +.TP \fBconstructor\fI argList bodyScript\fR . This creates or updates the constructor for a class. The formal arguments to @@ -110,6 +131,15 @@ below), this command creates private forwarded methods. .VE TIP500 .RE .TP +\fBinitialise\fI script\fR +.TP +\fBinitialize\fI script\fR +.VS TIP478 +This evaluates \fIscript\fR in a context which supports local variables and +where the current namespace is the instance namespace of the class object +itself. This is useful for setting up, e.g., class-scoped variables. +.VE TIP478 +.TP \fBmethod\fI name argList bodyScript\fR . This creates or updates a method that is implemented as a procedure-like @@ -396,7 +426,7 @@ Some of the configurable definitions of a class or object are \fIslotted definitions\fR. This means that the configuration is implemented by a slot object, that is an instance of the class \fBoo::Slot\fR, which manages a list of values (class names, variable names, etc.) that comprises the contents of -the slot. The class defines three operations (as methods) that may be done on +the slot. The class defines five operations (as methods) that may be done on the slot: .TP \fIslot\fR \fB\-append\fR ?\fImember ...\fR? @@ -407,6 +437,16 @@ This appends the given \fImember\fR elements to the slot definition. . This sets the slot definition to the empty list. .TP +\fIslot\fR \fB\-prepend\fR ?\fImember ...\fR? +.VS TIP516 +This prepends the given \fImember\fR elements to the slot definition. +.VE TIP516 +.TP +\fIslot\fR \fB\-remove\fR ?\fImember ...\fR? +.VS TIP516 +This removes the given \fImember\fR elements from the slot definition. +.VE TIP516 +.TP \fIslot\fR \fB\-set\fR ?\fImember ...\fR? . This replaces the slot definition with the given \fImember\fR elements. @@ -424,15 +464,52 @@ and these methods which provide the implementation interface: .TP \fIslot\fR \fBGet\fR . -Returns a list that is the current contents of the slot. This method must -always be called from a stack frame created by a call to \fBoo::define\fR or -\fBoo::objdefine\fR. +Returns a list that is the current contents of the slot, but does not modify +the slot. This method must always be called from a stack frame created by a +call to \fBoo::define\fR or \fBoo::objdefine\fR. This method \fIshould not\fR +return an error unless it is called from outside a definition context or with +the wrong number of arguments. +.RS +.PP +.VS TIP516 +The elements of the list should be fully resolved, if that is a meaningful +concept to the slot. +.VE TIP516 +.RE +.TP +\fIslot\fR \fBResolve\fR \fIslotElement\fR +.VS TIP516 +Returns \fIslotElement\fR with a resolution operation applied to it, but does +not modify the slot. For slots of simple strings, this is an operation that +does nothing, whereas for slots of classes, this maps a class name to its +fully-qualified class name. This method must always be called from a stack +frame created by a call to \fBoo::define\fR or \fBoo::objdefine\fR. This +method \fIshould not\fR return an error unless it is called from outside a +definition context or with the wrong number of arguments; unresolvable +arguments should be returned as is (as not all slot operations strictly +require that values are resolvable to work). +.RS +.PP +Implementations \fIshould not\fR enforce uniqueness and ordering constraints +in this method; that is the responsibility of the \fBSet\fR method. +.RE +.VE TIP516 .TP \fIslot\fR \fBSet \fIelementList\fR . Sets the contents of the slot to the list \fIelementList\fR and returns the empty string. This method must always be called from a stack frame created by -a call to \fBoo::define\fR or \fBoo::objdefine\fR. +a call to \fBoo::define\fR or \fBoo::objdefine\fR. This method may return an +error if it rejects the change to the slot contents (e.g., because of invalid +values) as well as if it is called from outside a definition context or with +the wrong number of arguments. +.RS +.PP +This method \fImay\fR reorder and filter the elements if this is necessary in +order to satisfy the underlying constraints of the slot. (For example, slots +of classes enforce a uniqueness constraint that places each element in the +earliest location in the slot that it can.) +.RE .PP The implementation of these methods is slot-dependent (and responsible for accessing the correct part of the class or object definition). Slots also have @@ -440,6 +517,14 @@ an unknown method handler to tie all these pieces together, and they hide their \fBdestroy\fR method so that it is not invoked inadvertently. It is \fIrecommended\fR that any user changes to the slot mechanism be restricted to defining new operations whose names start with a hyphen. +.PP +.VS TIP516 +Most slot operations will initially \fBResolve\fR their argument list, combine +it with the results of the \fBGet\fR method, and then \fBSet\fR the result. +Some operations omit one or both of the first two steps; omitting the third +would result in an idempotent read-only operation (but the standard mechanism +for reading from slots is via \fBinfo class\fR and \fBinfo object\fR). +.VE TIP516 .SH EXAMPLES This example demonstrates how to use both forms of the \fBoo::define\fR and \fBoo::objdefine\fR commands (they work in the same way), as well as @@ -496,6 +581,84 @@ oo::class create B { inst m1 \fI\(-> prints "red brick"\fR inst m2 \fI\(-> prints "blue brick"\fR .CE +.PP +.VS TIP478 +This example shows how to create and use class variables. It is a class that +counts how many instances of itself have been made. +.PP +.CS +oo::class create Counted +\fBoo::define\fR Counted { + \fBinitialise\fR { + variable count 0 + } + + \fBvariable\fR number + \fBconstructor\fR {} { + classvariable count + set number [incr count] + } + + \fBmethod\fR report {} { + classvariable count + puts "This is instance $number of $count" + } +} + +set a [Counted new] +set b [Counted new] +$a report + \fI\(-> This is instance 1 of 2\fR +set c [Counted new] +$b report + \fI\(-> This is instance 2 of 3\fR +$c report + \fI\(-> This is instance 3 of 3\fR +.CE +.PP +This example demonstrates how to use class methods. (Note that the constructor +for \fBoo::class\fR calls \fBoo::define\fR on the class.) +.PP +.CS +oo::class create DBTable { + \fBclassmethod\fR find {description} { + puts "DB: locate row from [self] matching $description" + return [my new] + } + \fBclassmethod\fR insert {description} { + puts "DB: create row in [self] matching $description" + return [my new] + } + \fBmethod\fR update {description} { + puts "DB: update row [self] with $description" + } + \fBmethod\fR delete {} { + puts "DB: delete row [self]" + my destroy; # Just delete the object, not the DB row + } +} + +oo::class create Users { + \fBsuperclass\fR DBTable +} +oo::class create Groups { + \fBsuperclass\fR DBTable +} + +set u1 [Users insert "username=abc"] + \fI\(-> DB: create row from ::Users matching username=abc\fR +set u2 [Users insert "username=def"] + \fI\(-> DB: create row from ::Users matching username=def\fR +$u2 update "group=NULL" + \fI\(-> DB: update row ::oo::Obj124 with group=NULL\fR +$u1 delete + \fI\(-> DB: delete row ::oo::Obj123\fR +set g [Group find "groupname=webadmins"] + \fI\(-> DB: locate row ::Group with groupname=webadmins\fR +$g update "emailaddress=admins" + \fI\(-> DB: update row ::oo::Obj125 with emailaddress=admins\fR +.CE +.VE TIP478 .SH "SEE ALSO" next(n), oo::class(n), oo::object(n) .SH KEYWORDS |