桌面和移动编译器的条件定义

Question

I am working on a cross platform library that should compile in both desktop and mobile compilers supported by Delphi. as we know strings in desktop is 1-based and mobile is 0-based. is there any defines in Delphi that I can use to separate code that will compile in desktop and mobile and is backwards compatible at least down to XE2.

something more like if defines desktop do this else if mobile do this.

sorry for bad formatting. typing from Mobile.

Delphi version XE7 up 1.

Answer 1

The conditionals are documented here: http://docwiki.embarcadero.com/RADStudio/en/Conditional_compilation_(Delphi)

I think that the answer to the question that you asked is that you should switch on the NEXTGEN conditional.

However, just because you are compiling for mobile (ie NEXTGEN ) does not mean that strings must zero based. Likewise there is no compulsion for desktop code to be one based. Zero based strings can be enabled/disabled with the $ZEROBASEDSTRINGS directive.

You really ought to try to avoid conditional compilation. Conditional compilation adds significant complexity, makes testing harder, and increases the risk off defects. I strongly recommend you try to avoid conditional compilation where possible.

So for each unit you should decide whether you are zero or one based and include the appropriate directive at the top of that unit. If you plan to use the one based RTL functions like Pos and Copy , be one based. Otherwise use the string helper (introduced in XE3) and be zero based. The decision isn't really related to whether or not your code targets desktop or mobile.

Finally, you say you want to support mobile on XE2, but the compiler there is FreePascal which uses one based strings. Supporting XE2 mobile is another layer of complexity.