How to: Use the #globaldefine Directive to Avoid Overwriting

Artikkeli
05/18/2015

Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

The #globaldefine directive is similar to the #define directive. The difference is that #define directives generally take precedence over #globalmacro directives. This is true regardless of which directive occurs first in the X++ code.

A #globaldefine never overwrites a #define directive that has both a macro name and a value. A #globaldefine can overwrite another #globaldefine.

A #define directive that has only a name does not overwrite a #globalmacro that has both a name and a value.

Tip

It is recommended that you use #define, and that you do not use #globaldefine. Use of #globaldefine can create uncertainty that makes code difficult to maintain.

Prerequisites

For this topic, you must understand the information in How to: Test a Macro Value.

Code Sample for #globaldefine

The following code sample shows a difference in the behavior of #define and #globaldefine. Following the code sample is a table explaining the conclusions from the output. The primary test case in the code sample is labeled 12.

    static void InteractDefineGlobalJob(Args _args)
    {
        ;
        // Pairs of #define - #globaldefine directives (same macro names).
        #define.11_DEFINEvalue_GLOBALnoval("11__DEFINE.")
        #globaldefine.11_DEFINEvalue_GLOBALnoval
    
        #define.12_DEFINEnoval_GLOBALvalue
        #globaldefine.12_DEFINEnoval_GLOBALvalue("12_GLOBAL.")
    
        #define.13_DEFINEvalue_GLOBALvalue("13__DEFINE.")
        #globaldefine.13_DEFINEvalue_GLOBALvalue("13_GLOBAL.")
    
        // Pairs of #globaldefine - #define directives.
        #globaldefine.27_GLOBALvalue_DEFINEnoval("27_GLOBAL.")
        #define.27_GLOBALvalue_DEFINEnoval
    
        #globaldefine.28_GLOBALnoval_DEFINEvalue
        #define.28_GLOBALnoval_DEFINEvalue("28__DEFINE.")
    
        #globaldefine.29_GLOBALvalue_DEFINEvalue("29_GLOBAL.")
        #define.29_GLOBALvalue_DEFINEvalue("29__DEFINE.")
    
        // Pairs of same directive types.
        #define.50_DEFINEvalue_DEFINEnoval("50__DEFINE 1.")
        #define.50_DEFINEvalue_DEFINEnoval
    
        #globaldefine.64_GLOBALvalue_GLOBALnoval("64_GLOBAL 1.")
        #globaldefine.64_GLOBALvalue_GLOBALnoval
    
        #globaldefine.65_GLOBALnoval_GLOBALvalue
        #globaldefine.65_GLOBALnoval_GLOBALvalue("65_GLOBAL 2.")
    
        #globaldefine.66_GLOBALvalue_GLOBALvalue("66_GLOBAL 1.")
        #globaldefine.66_GLOBALvalue_GLOBALvalue("66_GLOBAL 2.")
    
        // Infolog outputs.
    
        info(#11_DEFINEvalue_GLOBALnoval);
        info(#12_DEFINEnoval_GLOBALvalue);
        info(#13_DEFINEvalue_GLOBALvalue);
    
        info(#27_GLOBALvalue_DEFINEnoval);
        info(#28_GLOBALnoval_DEFINEvalue);
        info(#29_GLOBALvalue_DEFINEvalue);
    
        info(#50_DEFINEvalue_DEFINEnoval);
    
        info(#64_GLOBALvalue_GLOBALnoval);
        info(#65_GLOBALnoval_GLOBALvalue);
        info(#66_GLOBALvalue_GLOBALvalue);
    
    /*****************************  Actual Infolog output
    Message (09:31:26 pm)
    11__DEFINE.
    12_GLOBAL.
    13__DEFINE.
    27_GLOBAL.
    28__DEFINE.
    29__DEFINE.
    50__DEFINE 1.
    64_GLOBAL 1.
    65_GLOBAL 2.
    66_GLOBAL 2.
    *****************************/
    }

Explanation of Outputs and Conclusions

The following table explains the test case outcomes from the previous code sample. The explanations document the behavior of #globalmacro.

Test case	Explanation
13 and 29	Shows that #define usually takes precedence over #globaldefine, regardless of which directive occurs first in the X++ code. Test case 12 shows this is not always true.
12	Shows that #globaldefine overwrites #define when #globaldefine is giving a value to an existing macro that has no value. Test cases 13 and 29 are more common and realistic.
50 and 64	Shows that a #globaldefine that has a name but no value does not overwrite a #globaldefine that has both a name and a value. The same is true between a pair of #define directives. This resembles test case 12.
65 and 66	Shows that a #globaldefine that has both a name and a value overwrites a previous #globaldefine.

Different from #if Test Approach

The exact semantics of #globaldefine cannot be achieved through #if test directives. By using #if tests you can avoid overwriting a #define and a #globaldefine. But #if tests cannot distinguish between #define and #globaldefine macros.

The following code sample is the closest you can come to achieving the #globaldefine semantic with other directives such as #if.

static void IfNotDefineNestGlobalJob (Args _args)
    {
        ;
        #undef.MaybeMac
    
        #ifnot.MaybeMac
            #define.MaybeMac(4444) // Works.
        #endif
    
        #if.MaybeMac
            info(int2str(#MaybeMac));
        #endif
    
    /**********************  Actual Infolog output
    Message (07:43:32 pm)
    4444
    **********************/
    }

Jaa

How to: Use the #globaldefine Directive to Avoid Overwriting

Prerequisites

Code Sample for #globaldefine

Explanation of Outputs and Conclusions

Different from #if Test Approach

See also

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