JSON, Level: Advanced, Version: FM 16 or later

Ordering Elements within JSON Objects

Introduction

If you’ve generated JSON objects via FileMaker, you’re likely aware of the disparity between the order in which you specify the elements, and the order in which they subsequently appear (i.e., alphabetized by key name). As I wrote two years ago (in Thinking About JSON, Part 2)…

Both JSONSetElement and JSONFormatElements will automatically alphabetize key/value pairs within JSON objects. This can be disconcerting if you aren’t expecting it, but eventually you work through the stages of grief and come to accept that it’s just the way things are. The JSON Data Interchange Standard definition at json.org specifies that “An object is an unordered [emphasis mine] set of name/value pairs”, whereas an array is an “ordered collection of values”. In other words, by definition the order of the key/value pairs within JSON objects simply does not, and should not, matter.

Well… okay… you know that, and I know that, and FileMaker knows that, as do the JSON Jedi… but what if you are demonstrating a proof of concept to a client, and to avoid cognitive dissonance and unnecessary explanation you’d like to “doctor the evidence” (so to speak) and order the elements meaningfully?

For example, you’d like them to see this…

2020-04-29_165223 Continue reading “Ordering Elements within JSON Objects”

JSON, Level: Advanced, Version: FM 18 or later, Virtual List

Virtual Portal, part 2

[Note: several hours after posting this article I realized the “Hide Object” calc could be streamlined. Screen shot and demo have been updated to reflect this.]

Demo file: virtual-portal-v2b.zip (requires FM 18 or later)

This is a quick follow up to the Virtual Portal article I posted the other day. As you may recall, the objective was to use virtual list to display disparate entities in a portal…

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…via an array like this…

2020-02-16_18-29-04 Continue reading “Virtual Portal, part 2”

ExecuteSQL, JSON, Level: Advanced, Version: FM 16 or later, Virtual List

Virtual Portal

Demo file: virtual-portal-v1b.zip

This is a follow-up to last month’s article on virtual list, and this time we’re going to explore a way to use virtual list in a portal.

Imagine you have built a system where a Company can be a parent of a Mill, Refinery, Estate, or another Company.

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Each of these entities exists as a separate table in your database…

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…and from the perspective of a Company record, you’d like to be able to see all immediate children. Continue reading “Virtual Portal”

JSON, Level: Advanced, Version: FM 18 or later

FM18: JSON.InsertArrayElement

Disclaimer: the technique shown in this article is provided on an as-is basis. Use with appropriate caution and at your own risk.

Demo file: JSON-Array-Custom-Functions.zip (requires FM 18 or later)

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Have you ever noticed that FileMaker does not provide a JSON function to insert a new element into an existing array? For example, given this array (and bearing in mind that JSON uses a zero-based index)…

[ “A” , “B” , “C” , “D” ]

…JSONSetElement ( array ; 2 ; “XXX” ) will transform it to…

[ “A” , “B” , “XXX” , “D” ]

… but we have no native JSON function to “push” a new element into position 2 so that existing elements slide one position rightward to accommodate, like so:

[ “A” , “B” , “XXX” , “C” , “D” ]

Continue reading “FM18: JSON.InsertArrayElement”

JSON, Level: Advanced, Version: FM 18 or later

FM18: JSON.UpdateArrayElement

Disclaimer: the technique shown in this article is an attempt to work around an annoyance that can crop up when using FileMaker’s native JSONSetElement function, and is provided on an as-is basis. Use with appropriate caution and at your own risk.

Acknowledgement: I owe a debt of gratitude to Paul Jansen for many illuminating JSON-related discussions over the last year or so. Thank you Paul.

Bug fixes: Demo file has been updated to v3.

Introduction

Today we’re going to look at a custom function, JSON.UpdateArrayElement, written to circumvent a problem you may encounter when using JSONSetElement. (Note: see Thinking About JSON, part 1 and part 2 if you need a basic FM/JSON overview or refresher.)

Demo file: JSON-UpdateArrayElement-v3.zip (requires FM 18 or later)

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Why did I write a custom function to do what JSONSetElement apparently already does? Because under certain circumstances JSONSetElement does not work the way I believe it should. We’ll get to the custom function in a minute, but first there are a couple issues we need to examine. Continue reading “FM18: JSON.UpdateArrayElement”

JSON, Level: Advanced, Version: FM 16 or later

Magic Portals

Today we’re going to look at a design pattern I’ve recently been using to accommodate a client request. The request is to be able to view and edit a parent, all related children, and all related grandchildren via a single “flattened” interface.

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Demo file: magic-portals.zip (requires FM 16 or later) Continue reading “Magic Portals”

FM Development, JSON, Level: Intermediate, Version: FM 16 or later

Creating and Using Invisible Window IDs

Editor’s note: I first became aware of Paul Jansen when I licensed his FMTools in the late 1990s, and I finally had the pleasure of meeting him last June at dotFMP after 20 years of online and voice communication. It’s an honor and a privilege to welcome him to FileMaker Hacks as a guest author.

FileMaker is pretty flexible. As developers we are given options as to how to reference things; fields, scripts and layouts can be referenced by name or number/id. Whilst we know that referencing things by name is more fragile, it is still a very useful capability to have, but it is definitely more robust to reference by ID…

Windows are a bit of an odd one out; we can only reference them by name.

As windows are probably the most likely things to have their names changed during normal day to day usage of a FileMaker Database it would be really useful if we could keep track of them by an ID independent of the displayed window title. Another benefit of having access to an ID to identify a window is that we then have to option to very easily store and access window specific variables. Kevin has made use of window specific variables based upon the window name in several articles and I suggest that access to a numeric ID that was independent of the window title would be an improvement. Continue reading “Creating and Using Invisible Window IDs”

JSON, Level: Intermediate, Version: FM 16 or later, Virtual List

Faux Subsummaries via JSON + Virtual List

Today we’re going to take another look at a challenge we discussed last time (in Conditional Summary Report Header)… namely how to cajole FileMaker into displaying a subsummary, or a reasonable facsimile thereof, at the top of a report page when items in the group begin on an earlier page.

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Demo file: Faux Subsummaries via JSON + Virtual List

2018-10-15_09-54-56.png Continue reading “Faux Subsummaries via JSON + Virtual List”

JSON, Level: Intermediate

Thinking About JSON, part 3

This a quick followup to last month’s part 2, because today I want to to dig a little deeper into JSONSetElement and take a closer look at the first argument:

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As I wrote last time…

Part of what makes JSONSetElement so powerful is that it can be used both to create new entries, and to update existing entries. Specify a valid address, and it will either create the entry if it doesn’t already exist, or update it if it does.

Let’s talk about the update aspect first, because it’s extremely straight forward. If you have existing JSON in a variable, for example $$simpleJSON, you can update it (i.e., add new elements or change existing elements) like so:

    • JSONSetElement ( $$simpleJSON ; etc )

In other words, you use your existing JSON as the first argument.

But when it comes to creating new JSON, there are three possible first arguments to consider.

    • JSONSetElement ( “{}” ; etc )
      …instructing FileMaker to create a JSON object
    • JSONSetElement ( “[]” ; etc )
      …instructing FileMaker to create a JSON array
    • JSONSetElement ( “” ; etc )
      …trusting FileMaker to figure out which structure to create

At the risk of stating the obvious, in the first two cases we are being explicit, but in the third case we are not. (Note: If you’re unclear on the distinction between objects and arrays, this was covered in great detail in part 1.)

Continue reading “Thinking About JSON, part 3”

JSON, Level: Intermediate, Version: FM 16 or later

Thinking About JSON, part 2

This is a follow up to Thinking About JSON, part 1. Last time we were primarily concerned with learning about JSON paths and structures, and reading JSON. This time around we’re going to look at creating and manipulating JSON.

Demo file: winery-json.zip

(If the above screen shot looks familiar you have a good memory, because today’s demo is based on the one that accompanied this article: Summary List Fields in FM 13.)

To briefly recap, JSON is built on two structures…

  • Objects: surrounded by {} and consisting of comma-separated key:value pairs
    Simple example:  { “product” : “FileMaker Pro” , “version” : 17 }
  • Arrays: surrounded by [] and consisting of comma-separated values
    Simple example:  [ 2 , 4 , 6 ]

…and where things get interesting is that the “values” in either of the above structures can themselves be JSON (i.e., an object or an array). This defining feature of JSON, whereby a JSON structure can, and frequently does, contain embedded smaller JSON structures, was explored in detail in part 1, and we will see some examples of this today as well. Continue reading “Thinking About JSON, part 2”