While XOTcl 1 had very limited forms of parameters, XOTcl 2 and nx +provide a generalized and highly orthogonal parameter handling with +various kinds of value constraints. We devide the parameters into +Object Parameters (parameters used for initializing objects and +classes) and Method Parameters (parameters passed to +methods). Furthermore, XOTcl 2 and NX support return value checker +based on the same mechanisms.
- Class Foo -slots { - Attribute a - Attribute b -default 1 -} +# Object parameter specified as a list (short form) +# "a" has no default, "b" has default "1" +Class create Foo -attributes {a {b 1}} + # Create instance of the class Foo -Foo f1 -a 0 +Foo create f1 -a 0 -# Object f1 has a == 0 and b == 1 - |
+# Object f1 has a == 0 and b == 1|
- Class create Foo -attributes {a {b 1}} +# Object parameter specified via slots +Class Foo -slots { + Attribute a + Attribute b -default 1 +} + # Create instance of the class Foo -Foo create f1 -a 0 +Foo f1 -a 0 -# Object f1 has a == 0 and b == 1
+# Object f1 has a == 0 and b == 1
+ |
+
- Class create Foo { +# Object parameter specified via attribute methods +# (allow method modifieres and scripted configuration) + +Class create Foo { :attribute a :attribute {b 1} } @@ -1654,7 +1677,10 @@ by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -Class Person -slots { +# Object parameter with configured slot, defining an attribute +# specific type checker + +Class Person -slots { Attribute create sex -type "sex" { my proc type=sex {name value} { switch -glob $value { @@ -1670,7 +1696,10 @@ by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -Class create Person { +# Object parameter with scripted definition, defining an attribute +# specific type checker + +Class create Person { :attribute sex { :type "sex" :method type=sex {name value} { @@ -1695,10 +1724,16 @@ by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -# Predefined value constraints: object, class, alnum, alpha, -# ascii, boolean, control, digit, double, false, graph, -# integer, lower, print, punct, space, true, upper, -# wordchar, xdigit +# Predefined value constraints: +# object, class, alnum, alpha, ascii, boolean, control, +# digit, double, false, graph, integer, lower, print, +# punct, space, true, upper, wordchar, xdigit +# +# User defined value constraints are possible. +# All parameter value checkers can be turned on and off. +# +# Define a boolean attribute and an integer attribute with a +# default Class create Foo -attributes { a:boolean @@ -1726,10 +1761,13 @@ by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -# Required parameter +# Required parameter: +# Define a required attribute a and a required boolean +# attribute b + Class create Foo -attributes { - a:boolean,required - {b:integer 1} + a:required + b:boolean,required } Class create Foo { - :attribute a:boolean,required - :attribute {b:integer 1} + :attribute a:required + :attribute b:boolean,required } |
- # Required parameter +# Parameter with multiplicity + Class create Foo -attributes { - ... - ints:integer,multivalued - {objs:object,multivalued ""} + {ints:integer,0..n ""} ;# list of integers, with default + objs:object,1..n ;# non-empty list of objects + obj:object,0..1 ;# single object, maybe empty } Class create Foo { - ... - :attribute ints:integer,multivalued - :attribute {objs:object,multivalued ""} + :attribute {ints:integer,0..n ""} + :attribute objs:object,1..n + :attribute obj:object,0..1 } |
## allowempty
The method parameters specifications in XOTcl 1 were limited and +allowed only value constraints for non positional arguments. NX and +XOTcl 2 provide value constraints for all kind of method parameters. +While XOTcl 1 required non-positional arguments to be listed in front of +positional arguments, this limitation is lifted in XOTcl 2.
| XOTcl | +Next Scripting Language | +
|---|---|
+
+ # Define method foo with non-positional parameters +# (x, y and y) and positional parameter (a and b) + +Class C +C instproc foo {-x:integer -y:required -z a b} {....} +C create c1 + +# invoke method foo +c1 foo -x 1 -y a 2 3 |
+
+
+ # Define method foo with non-positional parameters +# (x, y and y) and positional parameter (a and b) + +Class create C { + :public method foo {-x:integer -y:required -z a b} {....} + :create c1 +} +# invoke method foo +c1 foo -x 1 -y a 2 3 |
+
+
+ # n.a. |
+
+
+ # Define various forms of parameters not available in XOTcl 1 + +Class create C { + # trailing (or interleaved) non-positional parameters + :public method m1 {a b -x:integer -y} {....} + + # postional parameters with value constraints + :public method m2 {a:integer b:boolean} {....} + + # optional postional parameter (trailing) + :public method set {varName value:optional} {....} + + # parameter with multiplicty + :public method m3 {-objs:object,1..n c:class,0..1} {....} + + # In general, the same list of value constraints as for + # object parameter is available (see above). + # + # User defined value constraints are possible. + # All parameter value checkers can be turned on and off. +} |
+
todo
Return value checker are a functionality that was not yet available in +XOTcl 1. A return value checker assures that a method returns always a +parameter of a certain value. Return value checkers can be defined on +all forms of methods. Like for other value checkers, return +value checkers can be turned on and off.
| XOTcl | +Next Scripting Language | +
|---|---|
+
+ # n.a. |
+
+
+ # Define method foo with non-positional parameters +# (x, y and y) and positional parameter (a and b) + +Class create C { + # Define method foo which returns an integer value + :method foo -returns integer {-x:integer} {....} + + # Define an alias for the Tcl command ::incr + # and assure, it always returns in integer + :alias incr -returns integer ::incr + + # Define a forwarder that has to return integer + :forward ++ -returns integer ::expr 1 + + + # Define a method that has to return a non-empty + # list of objects + :public class-object method instances {} -returns object,1..n { + return [:info instances] + } +} |
+
The following changes for parameters could be regarded as bug-fixes.