Problems related to object non-existent

If the object does not exist, have you ever encountered this problem "calltoamemberfunctiongetmermeridfieldname () onanon-objectin"? this problem may be caused by the absence of the necessary class library file, including introduction, and the object does not exist?
Have you ever encountered this situation: "Call to a member function getCustomerIdFieldName () on a non-object in"

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This problem may be caused by the absence of the necessary class library file, including introduction. check the header introduction carefully or whether the getCustomerIdFieldName () function is defined.
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Discussion

Reference:

This problem may be caused by the absence of the necessary class library file, including introduction. check the header introduction carefully or whether the getCustomerIdFieldName () function is defined.


Print_r ($ this-> _ getResource () is used to print detailed information of the class. This is used to obtain information about the class.