使用PB未公开的INDIRECT关键字

作者：Réal Gagnon

 

INDIRECT declaration statement enables a function to be called indirectly by simply setting an instance or shared variable. With a simple INDIRECTed variable, we need to provide 2 functions. One to set the value and one to retrieve the value.

[instance variable]public: INDIRECT string i_username {of_SetUsername(*value),of_GetUsername()}private: string zis_username[Powerscript functions]function integer of_SetUsername(string as_username)    IF NOT IsNull(as_username) THEN       zis_username = upper(as_username)    END IF    RETURN 1function String of_GetUsername()    RETURN zis_username[test code]// the of_SetUsername() function is called by PBi_username = "powerbuilder howto"// the of_GetUsername() function is called by PBMessageBox("username", i_username) 

Here some notes from Jeremy Lakeman (thanks!).

• INDIRECT variables only compile with 2 or 6 functions in the array otherwise the compiler will crash.
• Arguments that start with a * will be replaced by the appropriate value at compile time and all arguments are optional, the compiler wont complain if you don't pass one of the valid values
• Arguments can be supplied in any order
• The compiler will crash if you define a function with an unsuported argument
• Extra identifiers can be passed to each method, but only if they are valid in the context of the calling code
• The argument names are :
  string *name the name of the variable (used with INDIRECT array)
  any *value the value being assigned
  long[] *args the array of array dimensions (used with INDIRECT array)
• Where a value is supplied as an argument, the compiler will call any matching method. This means that you could override the set methods to allow multiple types of values to be assigned.

INDIRECT keyword when used with an array is a little bit more tricky, we need to define 6 functions.

In the following example, the INDIRECT array converts its member to uppercase. A userobject is used to hold our INDIRECT array and the 6 required functions.

[EXPORT .sru file, save into a file _n_cst_indirect.sru_ and then IMPORT it in PB]

$PBExportHeader$n_cst_indirect.sruforwardglobal type n_cst_indirect from nonvisualobjectend typeend forwardglobal type n_cst_indirect from nonvisualobjectend typeglobal n_cst_indirect n_cst_indirecttype variablesindirect string x[] {&        of_set_array(*name, *value), &        of_set_item(*name, *args, *value), &        of_get_array(*name), &        of_get_item(*name, *args), &        of_upperbound(), &        of_lowerbound()}private:string ix[]end variablesforward prototypespublic function integer of_lowerbound ()public function integer of_upperbound ()private function any of_get_array (string s)private function string of_get_item &              (string s, long al_dimensions[])private subroutine of_set_item &    (string s, long al_dimensions[], string as_value)private subroutine of_set_array (string s, string as_values[])end prototypespublic function integer of_lowerbound ();// provide the lower bound of the array// can be defined with a *value argument// but then must be called by lowerbound(x, 1)// this method must be publicreturn lowerbound(ix)end functionpublic function integer of_upperbound ();// provide the upper bound of the array// can be defined with a *value argument// but then must be called by upperbound(x, 1)// this method must be publicreturn upperbound(ix)end functionprivate function any of_get_array (string s);// return the entire array in an any variableany la_retla_ret=ixreturn la_retend functionprivate function string of_get_item &     (string s, long al_dimensions[]);// get an element of the arrayreturn ix[al_dimensions[1]]end functionprivate subroutine of_set_item &     (string s, long al_dimensions[], string as_value);// set an element of the arrayix[al_dimensions[1]]=upper(as_value)end subroutineprivate subroutine of_set_array (string s, string as_values[]);integer iString ls_blank[]ix = ls_blank// set the entire arrayFOR i = 1 TO upperbound(as_values)   x[i] = as_values[i]NEXTend subroutineon n_cst_indirect.createcall super::createTriggerEvent( this, "constructor" )end onon n_cst_indirect.destroyTriggerEvent( this, "destructor" )call super::destroyend onTo use the userobject from Powerscript :integer in_cst_indirect lnv_iString tmp[] = &  { "the uppercase conversion", &  "was done with the", &  "INDIRECT keyword!"}lnv_i = create n_cst_indirectlnv_i.x[1] = "powerbuilder howto"MessageBox("", lnv_i.x[1])lnv_i.x[2] = "http://www.rgagnon.com"MessageBox("", lnv_i.x[2])Messagebox("", string(upperbound(lnv_i.x)))lnv_i.x = tmpFOR i = 1 TO Upperbound(lnv_i.x)   MessageBox("", lnv_i.x[i])NEXT 

The same technique but this time, our array type is long.

$PBExportHeader$n_cst_indirect.sruforwardglobal type n_cst_indirect from nonvisualobjectend typeend forwardglobal type n_cst_indirect from nonvisualobjectend typeglobal n_cst_indirect n_cst_indirecttype variablesindirect long x[] {&        of_set_array(*name, *value), &        of_set_item(*name, *args, *value), &        of_get_array(*name), &        of_get_item(*name, *args), &        of_upperbound(), &        of_lowerbound()}private:long ix[]end variablesforward prototypespublic function integer of_lowerbound ()public function integer of_upperbound ()private function any of_get_array (string s)private subroutine of_set_array (string s, long al_values[])private function long of_get_item (string s, long al_dimensions[])private subroutine of_set_item &    (string s, long al_dimensions[], long al_value)end prototypespublic function integer of_lowerbound ();return lowerbound(ix)end functionpublic function integer of_upperbound ();return upperbound(ix)end functionprivate function any of_get_array (string s);any la_retla_ret=ixreturn la_retend functionprivate subroutine of_set_array (string s, long al_values[]);ix=al_valuesend subroutineprivate function long of_get_item (string s, long al_dimensions[]);return ix[al_dimensions[1]]end functionprivate subroutine of_set_item &        (string s, long al_dimensions[], long al_value);ix[al_dimensions[1]]=al_valueend subroutineon n_cst_indirect.createcall super::createTriggerEvent( this, "constructor" )end onon n_cst_indirect.destroyTriggerEvent( this, "destructor" )call super::destroyend on 

Array with multi-dimensions needs functions with different signatures :

$PBExportHeader$n_cst_indirect.sruforwardglobal type n_cst_indirect from nonvisualobjectend typeend forwardglobal type n_cst_indirect from nonvisualobjectend typeglobal n_cst_indirect n_cst_indirecttype variablesindirect long x[1,2,3] {&        of_set_array(*name, *value, *eoseq), &        of_set_item(*name, *nargs, *args, *value, *eoseq), &        of_get_array(*name, *eoseq), &        of_get_item(*name, *nargs, *args, *eoseq), &        of_upperbound(*dims), &        of_lowerbound(*dims)}private:long ix[]/*    indirect variables only compile with 2 or 6 functions in the array    otherwise the compiler will crash    arguments that start with a * will be replaced by the appropriate    value at compile time    all arguments are optional, the compiler wont complain if you don't    expect one of the valid values    arguments can be supplied in any order    the compiler will crash if you define a function with an unsuported    argument    extra identifiers can be passed to each method, but only if they are    valid in the context of the calling code    Eg you could pass "this" as an argument    string  *name   the name of the variable    any     *value  the value being assigned    long[]  *args   the array of array dimensions    long    *nargs  the number of elements in *args    boolean *eoseq  end of sequence                      used to indicate if this is the end of a dot notation                      sequence    integer *dims   dimension for lower or upper bound?                      the compiler doesn't seem to care which named value                      you actually use though    Where a value is supplied as an argument, the compiler will call any    matching method. This means that you could override the set methods    to allow multiple types of values to be assigned.*/end variablesforward prototypespublic function integer of_upperbound (integer al_dims)public function integer of_lowerbound (integer al_dims)private subroutine of_set_array &   (string as_name, long al_values[], boolean ab_eoseq)private function any of_get_array (string as_name, boolean ab_eoseq)private function long of_get_item &   (string as_name, long al_n_dimensions, &    long al_dimensions[], boolean ab_eo_seq)private subroutine of_set_item &  (string as_name, long al_n_dimensions, &   long al_dimensions[], long al_value, boolean ab_eoseq)end prototypespublic function integer of_upperbound (integer al_dims);// provide the upper bound of the array// can be defined with a * argument doesn't seem to care which one// but then must be called by upperbound(x, 1)// this method must be publicreturn upperbound(ix)end functionpublic function integer of_lowerbound (integer al_dims);// provide the lower bound of the array// can be defined with a * argument doesn't seem to care which one// but then must be called by lowerbound(x, 1)// this method must be publicreturn lowerbound(ix)end functionprivate subroutine of_set_array &    (string as_name, long al_values[], boolean ab_eoseq);// set the entire arrayix=al_valuesend subroutineprivate function any of_get_array (string as_name, boolean ab_eoseq);// return the entire array in an any variableany la_retla_ret=ixreturn la_retend functionprivate function long of_get_item &  (string as_name, long al_n_dimensions, long al_dimensions[],&    boolean ab_eo_seq);// get an element of the arrayreturn ix[al_dimensions[1]]end functionprivate subroutine of_set_item &  (string as_name, long al_n_dimensions, long al_dimensions[], &   long al_value, boolean ab_eoseq);// set an element of the arrayix[al_dimensions[1]]=al_valueend subroutineon n_cst_indirect.createcall super::createTriggerEvent( this, "constructor" )end onon n_cst_indirect.destroyTriggerEvent( this, "destructor" )call super::destroyend on 

 由 Ericwoo 在 六月 07, 2008 15:44 发贴 | 永久链接 | 删除 | 回复这个