https://forge.codesys.com/forge/talk/Engineering/thread/a09f75ccef/2020-02-27T13:47:44.430000ZRecent posts to Generic Change Log2020-02-27T13:47:44.430000Z2020-02-27T13:47:44.430000ZTim.Manninghttps://forge.codesys.com/u/tim-manning/https://forge.codesys.com4f23f1b83e8305cf5e4d91a7077df26c7f72a495

<div class="markdown_content"><p>I need to develop a generic change log.</p> <p>I want to be able to compare two instances of a structure (dutName and dutNameLast), and determine which elements have changed.</p> <p>I can use the MEM.Compare function to determine that there is a difference between the two instances of structures. </p> <p>But once I detect that there is a difference, I need to populate a Change Log, which will be an array of a structure that looks like this:</p> <p>ChangeTS | SeqNum | VarName | OldValue | NewValue<br/> DATE_AND_TIME | 123 | dutName.configINT_A | 'xxx' | 'xxy'<br/> DATE_AND_TIME | 122 | dutName.configREAL_B | 'x.xxxx' | 'y.yyyy'<br/> DATE_AND_TIME | 121 | dutName.configBOOL_C | '1' | '0'<br/> DATE_AND_TIME | 120 | dutName.configDINT_D | 'xxxxxx' | 'yyyxyy'</p> <p>Only the elements that have changed get logged.</p> <p>I want this to be generic, because I need to be able to compare two instances of a variety of structures. </p> <p>I am having trouble figuring out how to do the following:</p> <ol> <li> <p>Is there a programmatic way to determine what the element names are for a structure? I'd like to be able to reference the structure somehow, and get a list of element names returned. </p> </li> <li> <p>Is there an easy way to traverse the elements of a structure, so that I can do a comparison of the individual elements in some kind of loop:</p> </li> </ol> <p>Loop through the elements of the structure<br/> compare value of dutName.(nth_elementname) to value of dutNameLast.(nth_elementname)<br/> change <em>.(nth_elementname) to </em>.(nth+1elementname)<br/> End loop</p> <p>Any assistance or advice would be greatly appreciated.</p></div>