{"id":1572,"date":"2014-06-24T14:53:20","date_gmt":"2014-06-24T04:53:20","guid":{"rendered":"http:\/\/www.malcolmgroves.com\/blog\/?p=1572"},"modified":"2014-06-25T04:38:00","modified_gmt":"2014-06-24T18:38:00","slug":"no-code-calculated-fields-in-rad-studio-and-appmethod","status":"publish","type":"post","link":"http:\/\/www.malcolmgroves.com\/blog\/?p=1572","title":{"rendered":"“No Code” Calculated Fields in RAD Studio and AppMethod"},"content":{"rendered":"

In Perth last week I was showing the new FieldOptions property<\/a> on datasets. As part of the demo, I had to create a calculated field, and when I brought up the New Field dialog an audience member suggested I create an InternalCalc field instead.<\/p>\n

I’d never heard of an InternalCalc field at the time, so later I did some research into what they are. In FireDAC<\/a> they do everything a normal Calculated Field does, but in addition, you can define the value using the DefaultExpression property of the field, rather than having to write an OnCalcFields event handler.<\/p>\n

<\/p>\n

\"The<\/a><\/p>\n

The New Field dialog, showing the 5 different types of fields you can create<\/p>\n

In the Object Inspector screen shot below, you can see I have a TStringField with its FieldKind set to fkInternalCalc and the DefaultExpression set to:<\/p>\n

LAST_NAME + ', ' + FIRST_NAME<\/code><\/p>\n

\"Object<\/a>

Object Inspector showing the DefaultExpression and FieldKind properties of my InternalCalc field<\/p><\/div>\n

This not only lets me avoid adding code for simple field calculations, but further, the calculated value is visible at design-time, unlike normal calculated fields.<\/p>\n

\"The<\/a>

The InternalCalc field at design-time<\/p><\/div>\n

There are more details\u00a0in the docs here<\/a>\u00a0and more details on writing the expressions here<\/a>. On the same page it discusses Aggregated Fields, something else I haven’t played with. Have to add it to my list.<\/p>\n","protected":false},"excerpt":{"rendered":"

In Perth last week I was showing the new FieldOptions property on datasets. As part of the demo, I had to create a calculated field, and when I brought up the New Field dialog an audience member suggested I create an InternalCalc field instead. I’d never heard of an InternalCalc field at the time, so […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101,120],"tags":[103,19,48,102],"class_list":["post-1572","post","type-post","status-publish","format-standard","hentry","category-db","category-firemonkey","tag-appmethod","tag-delphi","tag-embarcadero","tag-firedac"],"_links":{"self":[{"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1572","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1572"}],"version-history":[{"count":7,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1572\/revisions"}],"predecessor-version":[{"id":1582,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1572\/revisions\/1582"}],"wp:attachment":[{"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1572"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1572"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.malcolmgroves.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1572"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}