Using Trim in ClientDataSet Filters

I announced in my last blog post that an updated version of Delphi in Depth: ClientDataSets is now available, both in printed and in eBook formats. In response, a reader posted this question as a comment:

I used TClientDataSet.Filter. CDS's Filter support "Trim" statement in Delphi help doc. It support "Trim(Name, '.')". But, how to used the statement?

Here is the answer. Imagine that your ClientDataSet includes a Company field, and that you have set the ClientDataSet's Filtered property to True, and have entered a Trim statement in the Filter property.

When you call Trim you can pass either one or two parameters. If you pass one parameter, you pass the name of a field. In response, Trim will remove any leading and trailing white spaces (please see the first comment below). For example, the filter Trim(Company) = 'Unisco' will trim white space, and the filtered data will include records whose Company field includes 'Unisco ', '    Unisco', '  Unisco  ', and 'Unisco'.

If you include the second, optional parameter, Trim will return the value of that field after removing that leading and/or trailing character. As a result, Trim(Company, 'o') = 'Unisc' will match on 'Unisco', 'oUnisc', and 'oUnisco. Likewise, Trim(Company, '.') = 'Unisco' will match on 'Unisco', '.Unisco', 'Unisco....', and '...Unisco.'.

There are two variations on Trim. These are TrimLeft and TrimRight. Like Trim, these functions can also take one or two parameters. If you call TrimLeft or TrimRight with only one parameter, those functions will remove white space from the beginning or the ending of the specified field, respectively. If you pass a second parameter, TrimLeft or TrimRight will remove that character from the beginning or ending of the specified field, respectively.

For example, TrimLeft(Company, 'U') = 'nisco' will match on a record whose Company field contains 'Unisco' and 'nisco'. Likewise, TrimRight(Company, 'o') = 'Unisc' will match on a record whose company field contains 'Unisc', 'Unisco', and even 'Uniscooo'.

Now Available: Delphi in Depth: ClientDataSets 2nd Edition

I published the original Delphi in Depth: ClientDataSets book back in March of 2011. At the time I believe it was my 24th book on computer software, though I must admit that I've lost count. Nonetheless, I greatly appreciated the many kind comments I've received from readers since its publication, even though it is a Delphi book "about one component."

I decided to update the code samples following the release of Delphi XE7. My original code samples made use of the Borland Database Engine and the sample Paradox tables that shipped with Delphi, which permitted those code samples to be compiled and run without any additional configuration, something that I felt was important.

Things changed with the release of Delphi XE7. The BDE is no longer installed by default. In addition, Delphi Professional (and higher) now ships with an alternative database solution that can be used without any additional configuration. This solution, which makes use of FireDAC and InterBase, did not exist when the first edition of this book was published.

Once I started updating the code samples to use FireDAC and InterBase, I realized that there were also a few additions that I could make to the original book. For example, the new FieldOptions property introduced to TDataSet in Delphi XE6 gave developers additional flexibility in their use of persistent fields, such as calculated and internal calc fields. A nod to LiveBindings would also be warranted.

It didn't take long before I concluded that it was time to give the book a good once over, tweaking the odd description here and there, adding material where appropriate, and correcting a few missed typos. And, of course, using the new FireDAC/InterBase examples in the book's code listings. I also updated all of the figures in the book to show the latest version of Delphi at the time of my writing (XE7). The original BDE/Paradox examples are still available for download, which is necessary in order to support older versions of Delphi, those prior to XE5. XE5 was the first version of FireDAC to use the new FD prefix in component names, as well as the new FireDAC unit names.

Permit me now to anticipate a question that is sure to come up. "What if I bought the original edition of Delphi in Depth: ClientDataSets? Should I buy the 2nd edition?" Well, you probably don't need to buy the 2nd edition unless you want to have the most current version on your bookshelf. In updating the 2nd edition I re-read, for the purpose of correcting and editing, every page of the original manuscript many times. And, for the most part, I was very happy with what I had written. As a result, there are large segments from the original text that are unchanged, or have inconsequential changes in the wording. Yes, I did add sections on FieldOptions, LiveBindings, and special filter operations. There are also a few additional examples and extended discussions.

I should also note that you can use the new FireDAC/InterBase samples with the original book. Visit the book's download site, listed in Appendix A of the original publication. There you will find the FireDAC/InterBase code sample download, along side the BDE/Paradox code download. Again, these FireDAC examples only work with Delphi XE5 and later, so the BDE-based examples are still available for use with earlier versions of Delphi.

I should also note that I removed three chapters that appeared at the end of the original book from the 2nd edition. Those chapters covered DataSnap, with a mix of COM-based DataSnap and the newer DataSnap introduced in Delphi 2009. While ClientDataSets played a central role in the COM-based DataSnap (the obsolete version), they are one of many options in the new DataSnap. In the end, I concluded that the DataSnap chapters were out of place.

I am releasing two versions of Delphi in Depth: ClientDataSets 2nd Edition. The printed version is available on CreateSpace and Amazon. And, in response to popular request, I am releasing a PDF version on FastSpring. You can find links to these releases from the book's web site at http://www.JensenDataSystems/cdsbook2.

I am very happy with how Delphi in Depth: ClientDataSets 2nd Edition turned out. I hope that you are too.

Publication Date: Jan 07 2015
ISBN/EAN13: 150584018X / 9781505840186
Page Count: 358 pages, 7.44" x 9.69"

Web Site: http://www.JensenDataSystems/cdsbook2

Delphi Developer Days 2015 Agenda Announced

Ray Konopka and I worked over the holidays to prepare the agenda for Delphi Developer Days 2015, and I am very happy with the content we have planned for this year's tour.

As usual, we have created a balanced program that offers something for every Delphi developer. We have sessions covering the VCL (Visual Component Library) as well as sessions on mobile/FireMonkey development. Some sessions cover some of Delphi's newest features, while others apply to nearly every version of Delphi. In the database realm, we have client/server sessions as well as sessions covering distributed (DataSnap and REST) topics. We even have sessions covering some of the third party tools that ships with Delphi, including CodeSite and Fast Report.

Ray Konopka is the world's leading expert on Delphi component creation, and is also an expert on user interface design, and we've ensured that these topics are represented in the agenda. Best of all, all of the topics that I've mentioned will be covered in the Delphi Developer Days book that all attendees receive. Ray and I are now turning our attention to writing that book, and it is a creative process to which I am looking forward.

Delphi Developer Days 2015 is visiting four cities in the United States, Europe, and Scandinavia between 13 April and 11 May. And, we are currently in our very early registration period, and you will save even more if you register and make payment by 23 January, 2015.

For complete information on Delphi Developer Days 2015 locations, the agenda, session descriptions, and discounts, please visit http://www.DelphiDeveloperDays.com. 

Space is limited. Register today to save your seat.