__if_not_exists Statement
The __if_not_exists statement tests whether the specified identifier exists. If the identifier does not exist, the specified statement block is executed.
__if_not_exists ( identifier ) {
statements
};
Caution
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To achieve the most reliable results, use the __if_not_exists statement under the following constraints. |
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Apply the __if_not_exists statement to only simple types, not templates.
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Apply the __if_not_exists statement to identifiers both inside or outside a class. Do not apply the __if_not_exists statement to local variables.
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Use the __if_not_exists statement only in the body of a function. Outside of the body of a function, the __if_not_exists statement can test only fully defined types.
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When you test for overloaded functions, you cannot test for a specific form of the overload.
The complement to the __if_not_exists statement is the __if_exists statement.
For an example about how to use __if_not_exists, see __if_exists Statement.
