Combining structs

Sometimes you may need to populate one struct with the contents of two or more other structs.

A typical piece of Java code would look like the following:

Figure 1. Example Java code for combining structs

        BankBranchStruct dtls = new BankBranchStruct();
AddressDtls      addressDtls = new AddressDtls();
BankBranchDtls   bankBranchDtls = new BankBranchDtls();

// Copy from the "AddressDtls" struct
dtls.addressLine1 = addressDtls.addressLine1;
dtls.addressLine2 = addressDtls.addressLine2;
dtls.addressLine3 = addressDtls.addressLine3;
dtls.addressLine4 = addressDtls.addressLine4;
dtls.cityCode     = addressDtls.cityCode;
dtls.countryCode  = addressDtls.countryCode;
dtls.postalCode   = addressDtls.postalCode;
dtls.regionCode   = addressDtls.regionCode;
dtls.
         addressVersionNo 
        = addressDtls.
         versionNo 
        ;

// Copy from the "BankBranchDtls" struct
dtls.bankBranchID = bankBranchDtls.bankBranchID;
dtls.bankID       = bankBranchDtls.bankID;
dtls.bankSortCode = bankBranchDtls.bankSortCode;
dtls.name         = bankBranchDtls.name;
dtls.versionNo    = bankBranchDtls.versionNo;

By explicitly mapping the BankBranchStruct.addressVersionNo attribute to the Address.versionNo in the assignable relationship the Java can now be written as:

Figure 2. Equivalent Java code for combining structs

// Copy from the "AddressDtls" struct
dtls.assign(addressDtls);

// Copy from the "BankBranchDtls" struct
dtls.assign(bankBranchDtls);

Note that in this case, the second assign does not overwrite the first as it happens to reference a different subset of fields, so the net effect is that the two struct contents are merged.