Dispatcher Pattern

====Dispatcher Pattern====
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<pre>
If cc < 500
  money=900
else
  if cc < 600 
    money=1200
  && ..... ç¥
  endif
endif
</pre>

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<pre>
do case
  case between( 0, 500 )
    money=900
  case between( 501, 599 )
    money=1200
  && ... ç¥
endcase
</pre>

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<pre>
*
* ITax.prg
*
DEFINE CLASS ITax as custom
  PROCEDURE Init()
    create cursor crTax( cc_lo I, cc_hi I, PrivateTax Y,  BusinesTax Y )
    insert into crTax values (    0,  500, $ 1620, $  900 )
    insert into crTax values (  501,  599, $ 2160, $ 1200 )
    insert into crTax values (  600, 1199, $ 4320, $ 2160 )
    insert into crTax values ( 1200, 1799, $ 7120, $ 3060 )
    insert into crTax values ( 1800, 2399, $11230, $ 6480 )
    insert into crTax values ( 2400, 2999, $15210, $ 9900 )
    insert into crTax values ( 3000, 4199, $28220, $16380 )
    insert into crTax values ( 4200, 5399, $46170, $24300 )
    insert into crTax values ( 5400, 6599, $69690, $33660 )
    insert into crTax values ( 6600, 7799, $117000, $44460 )
    insert into crTax values ( 7800, 9999999, $117000, $44460 )
  ENDPROC
  PROCEDURE Destroy()
    use in crTax
  ENDPROC
  PROCEDURE GetTax( cc, theKind )
    local ly_result
    local lc_oldalias
    lc_oldalias=alias()

    select("crTax")
    go top
    locate for between( cc, crTax.cc_lo, crTax.cc_hi )
    if found()
      ly_result=crTax.&theKind
    else
      ly_result=0
    endif

    select( lc_oldalias )
    return ly_result
  ENDPROC
  PROCEDURE GetPrivateTax( cc )
    return this.GetTax( cc, "PrivateTax" )
  ENDPROC
  PROCEDURE GetBusinessTax( cc )
    return this.GetTax( cc, "BusinesTax" )
  ENDPROC
ENDDEFINE
</pre>

<pre>
*
* test_itax.prg
*
LOCAL lo_obj
set procedure to itax.prg
lo_obj=createobject("ITax")
? lo_obj.GetPrivateTax( 1000 )
? lo_obj.GetBusinessTax( 2000 )
</pre>

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[[category:ä»¥VFPä»ç´¹Design Pattern]]