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Sharon wrote: > "wozza" <wozza96@_NO_SPAM_yahoo.com> wrote in message > news:42c5ab87$0$9732$afc38c87@news.optusnet.com.au... >> "Sharon" <Sharon669@hotmail.com> wrote in message >> news:evGnEznfFHA.3916@tk2msftngp13.phx.gbl... >>> I have a logical oop problem; I have an interface, and derived >>> classes >>> >>> The interface represents a general printer, and each class is a >>> specific printer >>> >>> >>> >>> The question is what is the correct way to get a new instance of a >>> printer by its name? >>> >>> Where should the getPrinterObject function be? >>> >> >> You have a separate PrinterFactory object that can return a >> reference to the correct type. > > shuld i add new PrinterFactory class ? Yes. [quoted text, click to view] > how do i implement it ? Depends on what you're trying to accomplish in the long term. Generally, you'd have the factory look up the right thing to instantiate, but look up from where is the main question. Perhaps just a case statement. But maybe you want something more dynamic, so you could have it load a new assembly from disk. So, generally, it's: 1. Receive request for creation of specific type. 2. Find specific type. 3. Create new instance of specific type. 4. Return new instance (via interface). -- Reginald Blue "I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup (originator of C++) [quoted at the 2003 International Conference on Intelligent User Interfaces]
[quoted text, click to view]
Sharon wrote: <code elided>> so it will be somthing like : > > Yup, that's the factory pattern. -- Reginald Blue "I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup (originator of C++) [quoted at the 2003 International Conference on Intelligent User Interfaces]
Hi all,
I have a logical oop problem; I have an interface, and derived classes The interface represents a general printer, and each class is a specific printer The question is what is the correct way to get a new instance of a printer by its name? Where should the getPrinterObject function be? Example: ifPrinter printerObj = getPrinterObject("EpsonP333"); printDocument.setDocument(d1); printerObj.printDocument(); interface IfPrinter { void printDocument(); void rollEmptyPage(); void cleanPrinterHead(); string getPrinterType(); } class Hpv40 : IfPrinter { public void printDocument(){ do Hpv40 printing ... } public string getPrinterType(){ return this.type;} } class EpsonP333 : IfPrinter { public void printDocument(){ do EpsonP333 printing ... } public string getPrinterType(){ return this.type;} } class Cannon512: IfPrinter { public void printDocument(){ do Cannon512 printing ... } public string getPrinterType(){ return this.type;} }
how do i implement it ?
shuld i add new PrinterFactory class ? [quoted text, click to view] "wozza" <wozza96@_NO_SPAM_yahoo.com> wrote in message news:42c5ab87$0$9732$afc38c87@news.optusnet.com.au... > "Sharon" <Sharon669@hotmail.com> wrote in message > news:evGnEznfFHA.3916@tk2msftngp13.phx.gbl... >> Hi all, >> >> I have a logical oop problem; I have an interface, and derived classes >> >> The interface represents a general printer, and each class is a specific >> printer >> >> >> >> The question is what is the correct way to get a new instance of a >> printer by its name? >> >> Where should the getPrinterObject function be? >> > > You have a separate PrinterFactory object that can return a reference to > the correct type. > >
Thank you !
[quoted text, click to view] "Reginald Blue" <Reginald_Blue@hotmail.com> wrote in message news:da4idn$o42$1@trsvr.tr.unisys.com... > Sharon wrote: >> so it will be somthing like : >> >> > <code elided> > > Yup, that's the factory pattern. > > -- > Reginald Blue > "I have always wished that my computer would be as easy to use as my > telephone. My wish has come true. I no longer know how to use my > telephone." > - Bjarne Stroustrup (originator of C++) [quoted at the 2003 > International Conference on Intelligent User Interfaces] > >
[quoted text, click to view]
"Sharon" <Sharon669@hotmail.com> wrote in message news:evGnEznfFHA.3916@tk2msftngp13.phx.gbl... > Hi all, > > I have a logical oop problem; I have an interface, and derived classes > > The interface represents a general printer, and each class is a specific > printer > > > > The question is what is the correct way to get a new instance of a printer > by its name? > > Where should the getPrinterObject function be? > You have a separate PrinterFactory object that can return a reference to the correct type.
so it will be somthing like :
ifPrinter printerObj = PrinterFactory.getPrinterObject("EpsonP333"); printDocument.setDocument(d1); printerObj.printDocument(); class PrinterFactory{ public IfPrinter getPrinterObject(string printerName){ if(printerName.equels("Hpv40") return new Hpv40(); else if(printerName.equels("EpsonP333") return new EpsonP333(); ..... } } interface IfPrinter { void printDocument(); void rollEmptyPage(); void cleanPrinterHead(); string getPrinterType(); } class Hpv40 : IfPrinter { public void printDocument(){ do Hpv40 printing ... } public string getPrinterType(){ return this.type;} } class EpsonP333 : IfPrinter { public void printDocument(){ do EpsonP333 printing ... } public string getPrinterType(){ return this.type;} } class Cannon512: IfPrinter { public void printDocument(){ do Cannon512 printing ... } public string getPrinterType(){ return this.type;} } [quoted text, click to view] "Reginald Blue" <Reginald_Blue@hotmail.com> wrote in message news:da4gcu$nlq$1@trsvr.tr.unisys.com... > Sharon wrote: >> "wozza" <wozza96@_NO_SPAM_yahoo.com> wrote in message >> news:42c5ab87$0$9732$afc38c87@news.optusnet.com.au... >>> "Sharon" <Sharon669@hotmail.com> wrote in message >>> news:evGnEznfFHA.3916@tk2msftngp13.phx.gbl... >>>> I have a logical oop problem; I have an interface, and derived >>>> classes >>>> >>>> The interface represents a general printer, and each class is a >>>> specific printer >>>> >>>> >>>> >>>> The question is what is the correct way to get a new instance of a >>>> printer by its name? >>>> >>>> Where should the getPrinterObject function be? >>>> >>> >>> You have a separate PrinterFactory object that can return a >>> reference to the correct type. >> >> shuld i add new PrinterFactory class ? > > Yes. > >> how do i implement it ? > > Depends on what you're trying to accomplish in the long term. Generally, > you'd have the factory look up the right thing to instantiate, but look up > from where is the main question. Perhaps just a case statement. But > maybe > you want something more dynamic, so you could have it load a new assembly > from disk. > > So, generally, it's: > > 1. Receive request for creation of specific type. > 2. Find specific type. > 3. Create new instance of specific type. > 4. Return new instance (via interface). > -- > Reginald Blue > "I have always wished that my computer would be as easy to use as my > telephone. My wish has come true. I no longer know how to use my > telephone." > - Bjarne Stroustrup (originator of C++) [quoted at the 2003 > International Conference on Intelligent User Interfaces] > > [quoted text, click to view] "Reginald Blue" <Reginald_Blue@hotmail.com> wrote in message news:da4gcu$nlq$1@trsvr.tr.unisys.com... > Sharon wrote: >> "wozza" <wozza96@_NO_SPAM_yahoo.com> wrote in message >> news:42c5ab87$0$9732$afc38c87@news.optusnet.com.au... >>> "Sharon" <Sharon669@hotmail.com> wrote in message >>> news:evGnEznfFHA.3916@tk2msftngp13.phx.gbl... >>>> I have a logical oop problem; I have an interface, and derived >>>> classes >>>> >>>> The interface represents a general printer, and each class is a >>>> specific printer >>>> >>>> >>>> >>>> The question is what is the correct way to get a new instance of a >>>> printer by its name? >>>> >>>> Where should the getPrinterObject function be? >>>> >>> >>> You have a separate PrinterFactory object that can return a >>> reference to the correct type. >> >> shuld i add new PrinterFactory class ? > > Yes. > >> how do i implement it ? > > Depends on what you're trying to accomplish in the long term. Generally, > you'd have the factory look up the right thing to instantiate, but look up > from where is the main question. Perhaps just a case statement. But > maybe > you want something more dynamic, so you could have it load a new assembly > from disk. > > So, generally, it's: > > 1. Receive request for creation of specific type. > 2. Find specific type. > 3. Create new instance of specific type. > 4. Return new instance (via interface). > -- > Reginald Blue > "I have always wished that my computer would be as easy to use as my > telephone. My wish has come true. I no longer know how to use my > telephone." > - Bjarne Stroustrup (originator of C++) [quoted at the 2003 > International Conference on Intelligent User Interfaces] > >
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