Specifying Managed Arrays as Function Parameters in C++
A More Intuitive WayWe're all professionals here and can learn to adapt to any new syntax that gets thrown our way. However, with just a couple of type definitions and a macro, we can make our code much more readable and intuitive. For example, instead of having to remember to use the __gc keyword with arrays of value type members, we can simply define a typedef for each desired type so that we can use the same syntax for either reference or value types. From there, we can specify a generic macro that takes the type name as a parameter so we don't have to remember the name of the typedef for each supported type. Here's how that would look:
#define MCArray(type) type##Array typedef int intArray __gc; typedef String* StringArray ; // .. add more typedefs here per your needs
Now, compare the following function signatures, standard Managed Extensions syntax vs. the MCArray macro:
// Returning arrays using the Standard Managed Extensions syntax int ReturnInt1() __gc String* ReturnString1()  // Returning arrays using the MCArray macro MCArray(int) ReturnInt2() MCArray(String) ReturnString2() // Passing arrays using the Standard Managed Extensions syntax void PassArrayOfReferenceTypes(String* strings) void PassArrayOfValueTypes(int numbers __gc) // Passing arrays using the MCArray macro void PassArrayOfReferenceTypes(MCArray(String) values) void PassArrayOfValueTypes(MCArray(int) values)
As you can see, MCArray macro provides several benefits, including the following:
- You don't have to remember which types require the pointer specification.
- You don't have to remember which types require the __gc keyword.
- You don't have to remember to place the square brackets nor where to place them.
About the Author
The founder of the Archer Consulting Group (ACG), Tom Archer has been the project lead on three award-winning applications and is a best-selling author of 10 programming books as well as countless magazine and online articles.
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