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September 27, 2020
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Specifying Managed Arrays as Function Parameters in C++

  • By Tom Archer
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A More Intuitive Way

We'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.

In summary, the MCArray is much closer to native C++ syntax, resulting in fewer mistakes and greater readability.

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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This article was originally published on July 12, 2004

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