error variable not declared

[aj2903]

hi..
In .h file I have declared

union Uni1{
int a_data;
float b_data;
}UTemp

union Uni1{
int a_data;
float b_data;
}UTemp

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In .cpp I want to access the variables in the union i.e UTemp.a or UTemp.b;

But while compiling error is generated :

error: a_data has not been declared.

error: a_data has not been declared.

Pls help