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Re: Interface and struct
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Re: Interface and struct -
03-31-2004
, 10:54 PM
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Hi Bill, The class is right. The interface declaration is more like Function UpdateBar(myBar as Bar) as boolean The problem is that it seems to me that Bar should no longer live in Foo, now that Foo is hiding behind an interface. ( The reason for this is that Foo is a data class using SQL Server objects and there is soon going to be an FooBrother that uses Oracle data objects. Only one of the two will be compiled depending on the installation.) So where to place Bar? As a number of calling classes want to use Bar it would seem ideal to me to place it in a module. But if I do that then the above declaration fails with can't expose a friend type. I have a working solution by getting Bar to bunk down in one of the calling classes, but it seems tacky. regards Bob "Bill McCarthy <no spam>" <bill_mcc @ iprimus.com.au> wrote in message news:uNBBaCyFEHA.3576 (AT) tk2msftngp13 (DOT) phx.gbl... Hi Bob, Do you mean you have : Class Foo Public Structure Bar ... End Structure End Class and you want to define an Interface, such as : Public IFace Function GetBar() as Foo.Bar End Interface If so, Foo must be Public. Alternatively, don't have Bar nested. Bill. "Bob Clegg" <bclegg (AT) clear (DOT) net.nz> wrote in message news:OoEhpzvFEHA.712 (AT) tk2msftngp13 (DOT) phx.gbl... Hi, I have a Data Class that declares a Public struct. It accepts instances of this struct in some of its function calls. I now want to put an interface between this class and the calling classes. I would like to move the struct out to the module that is housing the interface. But when I do this I get a scoping problem. The interface declaration of any function that is passing one of these structs complains that it can't expose a friend type publicly. I have tried putting the struct into the interface and I have also tried a public declaration in the module proper and another module. The only thing that seems to work but doesn't sit comfortably with me is to declare it public in one of the calling classes. Any thoughts? thanks Bob |
#2
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Hi Bob, nested classes and structures are only useful for hiding and access to the outer classes private scoped members. So, you are probably best NOT to nest the struct. eg: Class Foo: Implements IFace ... End Class Structure Bar .. End Sturcture Interface IFace .. End Interface That is, keep them all separate. I have a feeling you are use to structs being like UDT's in Vb6, which they are in many ways, but they are also more like a class in many ways too. Most importantly, they do not have to be declared inside a class, but can be declared just like any class can be. Bill "Bob Clegg" <bclegg (AT) clear (DOT) net.nz> wrote in message news:u3IZmE2FEHA.3880 (AT) TK2MSFTNGP09 (DOT) phx.gbl... Hi Bill, The class is right. The interface declaration is more like Function UpdateBar(myBar as Bar) as boolean The problem is that it seems to me that Bar should no longer live in Foo, now that Foo is hiding behind an interface. ( The reason for this is that Foo is a data class using SQL Server objects and there is soon going to be an FooBrother that uses Oracle data objects. Only one of the two will be compiled depending on the installation.) So where to place Bar? As a number of calling classes want to use Bar it would seem ideal to me to place it in a module. But if I do that then the above declaration fails with can't expose a friend type. I have a working solution by getting Bar to bunk down in one of the calling classes, but it seems tacky. regards Bob "Bill McCarthy <no spam>" <bill_mcc @ iprimus.com.au> wrote in message news:uNBBaCyFEHA.3576 (AT) tk2msftngp13 (DOT) phx.gbl... Hi Bob, Do you mean you have : Class Foo Public Structure Bar ... End Structure End Class and you want to define an Interface, such as : Public IFace Function GetBar() as Foo.Bar End Interface If so, Foo must be Public. Alternatively, don't have Bar nested. Bill. "Bob Clegg" <bclegg (AT) clear (DOT) net.nz> wrote in message news:OoEhpzvFEHA.712 (AT) tk2msftngp13 (DOT) phx.gbl... Hi, I have a Data Class that declares a Public struct. It accepts instances of this struct in some of its function calls. I now want to put an interface between this class and the calling classes. I would like to move the struct out to the module that is housing the interface. But when I do this I get a scoping problem. The interface declaration of any function that is passing one of these structs complains that it can't expose a friend type publicly. I have tried putting the struct into the interface and I have also tried a public declaration in the module proper and another module. The only thing that seems to work but doesn't sit comfortably with me is to declare it public in one of the calling classes. Any thoughts? thanks Bob |
#3
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Hi Bill, You are on the money. It is the way I am thinking about it. Yes. VB6 habits die hard. The struct can stand alone. Thanks. Bob "Bill McCarthy <no spam>" <bill_mcc @ iprimus.com.au> wrote in message news:%23ndToY6FEHA.4084 (AT) TK2MSFTNGP11 (DOT) phx.gbl... Hi Bob, nested classes and structures are only useful for hiding and access to the outer classes private scoped members. So, you are probably best NOT to nest the struct. eg: Class Foo: Implements IFace ... End Class Structure Bar .. End Sturcture Interface IFace .. End Interface That is, keep them all separate. I have a feeling you are use to structs being like UDT's in Vb6, which they are in many ways, but they are also more like a class in many ways too. Most importantly, they do not have to be declared inside a class, but can be declared just like any class can be. Bill "Bob Clegg" <bclegg (AT) clear (DOT) net.nz> wrote in message news:u3IZmE2FEHA.3880 (AT) TK2MSFTNGP09 (DOT) phx.gbl... Hi Bill, The class is right. The interface declaration is more like Function UpdateBar(myBar as Bar) as boolean The problem is that it seems to me that Bar should no longer live in Foo, now that Foo is hiding behind an interface. ( The reason for this is that Foo is a data class using SQL Server objects and there is soon going to be an FooBrother that uses Oracle data objects. Only one of the two will be compiled depending on the installation.) So where to place Bar? As a number of calling classes want to use Bar it would seem ideal to me to place it in a module. But if I do that then the above declaration fails with can't expose a friend type. I have a working solution by getting Bar to bunk down in one of the calling classes, but it seems tacky. regards Bob "Bill McCarthy <no spam>" <bill_mcc @ iprimus.com.au> wrote in message news:uNBBaCyFEHA.3576 (AT) tk2msftngp13 (DOT) phx.gbl... Hi Bob, Do you mean you have : Class Foo Public Structure Bar ... End Structure End Class and you want to define an Interface, such as : Public IFace Function GetBar() as Foo.Bar End Interface If so, Foo must be Public. Alternatively, don't have Bar nested. Bill. "Bob Clegg" <bclegg (AT) clear (DOT) net.nz> wrote in message news:OoEhpzvFEHA.712 (AT) tk2msftngp13 (DOT) phx.gbl... Hi, I have a Data Class that declares a Public struct. It accepts instances of this struct in some of its function calls. I now want to put an interface between this class and the calling classes. I would like to move the struct out to the module that is housing the interface. But when I do this I get a scoping problem. The interface declaration of any function that is passing one of these structs complains that it can't expose a friend type publicly. I have tried putting the struct into the interface and I have also tried a public declaration in the module proper and another module. The only thing that seems to work but doesn't sit comfortably with me is to declare it public in one of the calling classes. Any thoughts? thanks Bob |
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