BLOB

Learn how to fetch the BLOBs, pass their values in the CRUD requests, and manipulate BLOBs in the singleton resource fields.

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BLOB
Thursday, April 21, 2022PrintSubscribe
Lesson: BLOBs with RESTful API

Values of Binary Large Objects (BLOBs) are represented as resource URLs in the data. User identity must be specified in the Authorization header to get or change a BLOB. Hypermedia links to replace or delete BLOB values are included. Developers submit binary data as fields in the body property of the $app.restful method argument or as the named values in the multipart/form-data of HTTP requests.

Work with the BLOB resources like a pro.

RESTful API Engine identifies the user automatically when the host application is making a request. The cookie with the self-encrypted user access token provides the identity information.
RESTful API Engine identifies the user automatically when the host application is making a request. The cookie with the self-encrypted user access token provides the identity information.

Postman shows the BLOB fetched from the resource with the authorization key specified in the "x-api-key" query parameter. RESTful API Engine requires an access token or authorization key to be specified explicitly by the external applications.
Postman shows the BLOB fetched from the resource with the authorization key specified in the "x-api-key" query parameter. RESTful API Engine requires an access token or authorization key to be specified explicitly by the external applications.

The standalone single page application fetches the image of the product category on-demand when the category name is clicked. The app follows the hypermedia links to find the product category "picture" field value.
The standalone single page application fetches the image of the product category on-demand when the category name is clicked. The app follows the hypermedia links to find the product category "picture" field value.

Sunday, June 20, 2021PrintSubscribe
Drawing Pad

Taking photos in business apps often requires the visual annotation of the image. Another common scenario is sketching on the pre-defined template. Touch UI provides a built-in drawing pad that works seamlessly with the BLOB fields of your app. The feature is enabled by default and can be activated with a tap on the “Draw” button.


The drawing pad will be immediately displayed in fullscreen mode in response to the tap. It offers several tools: pen, highlighter, blur, and eraser with multiple levels of undo and redo. You can draw with a finger or a stylus compatible with the touch-screen device. Mouse pointers will also work. 

The “pen” and “highlighter” will impact the image as one would expect. The “blur” tool will blur the image contents. The “eraser” will remove the effect of the other tools.


Developers can handle the blobdrawtoolbox.app event triggered on the document and override the available tools and their properties such as the width of the stroke and the color choices. The toolbox property of the event provides access to the default tool configuration.

The drawing is composed of multiple layers. Saving of the drawing will compose the final image that will be submitted to the server when the data record is saved. The end user can perform multiple sessions of drawing prior to the submission since the layers remain preserved until the record has been saved.


Sketching on the template will require a default image to be provided. Create a custom script to handle the getdefaultblob.app event. The field property will indicate the name of the blob field that does not have a value. If e.blob.url or e.blob.icon properties are assigned in the event handler, then the corresponding image will be downloaded or a material icon will be drawn.


For example, the following handler will cause the framework to create a blue material icon for the category picture in the application.


The default image based on an icon may serve as a blob stub whenever the optional image is required. The end user may tap on the image and have it replaced with their by either taking a photo on the device or choosing a previously created image.



Tapping on the default blob image will always activate the drawing pad if the BLOB data field is tagged as image-user-defined-none. The end user will not be able to replace the template image.

The end users may take real-world photos and provide the visual comments with the drawing pad tools. Keep in mind that the huge photographs taken by modern day cameras will likely be redundant for business purposes. Make sure to specify the image-size-WxH tag to engage the image preprocessor to enforce the pre-defined image photo size and graphical annotations. 


Drawing pad provides a powerful tool for the line-of-business apps. Naturally it may not always be desirable to allow image alteration. Tag the blob data field as image-editor-none to disable the drawing pad.


By default the blob images are rendered as thumbnails. Tag the data fields as image-original-always if the original image must be displayed both when the users are viewing and editing the data. The field with the tag image-original-editing will show the original image if the blob is presented in the “edit” mode. End users may still download the original image when viewing the record.


The drawing pad will work on the small devices, tablets, and huge desktop monitors.
Thursday, May 30, 2019PrintSubscribe
VS 2019, Multi File Upload, Command Line Mode
Code On Time release 8.7.11.0 brings support for Visual Studio 2019, Multi-File Upload in Touch UI applications, and new command line options that allow creating apps with automated scripts.

Start using Visual Studio 2019 with your projects. The new development environment is fully integrated in the app generator. If you do have an existing project and want to migrate to the latest tools from Microsoft, then select the app on the start page of the generator and choose Open option. File Explorer will show the project files. Either delete the file with *.sln extension and regenerate your app or right-click the solution file, open it with Visual Studio 2019, select the solution file item in Solution Explorer, and press Ctrl+S.

Multi-file Upload is now available in Touch UI if you add Upload action to a compatible data controller. End users of your app will be able to choose multiple files to upload. The app will create a database record for each file, have the file submitted to the server, and persist it to the first BLOB field.


Command Line support is now available in the app generator.

Enter the following in the command line to generate a database app that works on mobile devices and in the web browser:

codeontime -Generate "c:\apps\myapp3" -DbConnection "Data Source=;Initial Catalog=northwind-cmd;Integrated Security=True;" -run

Build mobile and web database apps in seconds in command line. Use generated apps to validate your ideas, prototype data input forms, enter sample data, and much more. Apps built with Code On Time are metadata-driven. Create you own customization tools to invoke codeontime.exe in command line mode. The upcoming Code On Time v9 will be using command line mode extensively since the entire development environment is incorporated directly in the apps.


The following features and fixes also included in this release:
  • (Model Builder) All words in field labels are capitalized when a model is created.
  • (Touch UI) Optimized packaging of JSON properties of FieldValue object instances to minimize footprint for offline/disconnected logging.
  • (Client Library) Values of static Check Box List are correctly displayed when more than one item is selected.
  • (Framework) Blob adapter configuration is not included in the JSON controller descriptor.
  • (Touch UI) Selection of files in BLOB input will make the input focused.
  • (Framework) New TemporaryFileStream class is used for temporary storage of BLOB content.
  • (Touch UI) Method $app.confim support chained alternative execution of code with promises when confirmation is canceled.
  • (Offline Sync) Concurrent uploading of BLOBs is implemented with optional reconciliation of failed to upload blobs.
  • (Offline Sync) End user can opt to sync without data refresh. The option will remain selected until data refresh is explicitly requested. This makes possible working offline and only uploading changes to the server.
  • (Framework) Batch Editing of many-to-many fields works correctly when the primary key field is explicitly included in the view.
  • (Framework) Batch Editing will not erase values of many-to-many fields that are not selected in the Batch Edit form.
  • (Framework) Surveys accept inline functions and non-string values as "Visible When" and "Read Only When" expressions in questions and topics.
  • (Framework) Signature prompt is vertically aligned to the middle.
  • (Touch UI) Download icon is not displayed anymore next to "DOWNLOAD" button.
  • (Offline Sync) Added support for signatures.
  • (Touch UI) Placing $none in "Notify" property of action will prevent notification from being displayed.
  • (ODP) Completed implementation of thumbnail production on the client.
  • (Model Builder) New implementation of multi-level construction of Copy property of lookups for both 1-to-Many and 1-to-1 relationships.
  • (Classic) Implementation of BLOB uploading is now moved to Offline Data Processor.
  • (Framework) Download cookie is set on the server only when specified in the request.
  • (Framework) Azure Blob Adapter now uses HTTPS by default.
  • (Touch UI) Fixed signature resizing.
  • (Model Builder) "Enter" key in the property of the last field will post changes and re-select the same field property.
  • (Localization) Italian localization contributed by Massimo Ciurleo.
  • (ODP) Signatures in child data views are fully supported in transactional mode (when odp is enabled).
  • (Project Wizard) New "Addons" section in Features.
  • (Framework) Filter expression in the model will not cause errors when advanced search is executed.
  • (Framework) Default transaction scope is "sequence",
  • (Offline Sync) If transaction scope is "sequence" then ODP-assigned sequence is overridden with an offline sequence number. If transaction scope is explicitly set to "all", then the sequence is assigned to 0 for all transactions in the log.
  • (Touch UI) Button "driving directions" correctly composes Google Maps query based on fields tagged as map-latitude and map-longitude.
  • (Client Library)  Failed blob will be abandoned since there is not much that the user can do. The row was either inserted or updated already. The blob was rejected by the server. Abandoning of blob eliminates infinite loop of submission.
  • (Framework) A registration record for on-demand fields with blank "On Demand Handler" is not generated in Blob.generated.cs(vb) to prevent duplicate "empty" handlers when more than one such field is defined.
  • (Classic) Rich Text editor correctly sets the value produced in custom editors.
  • (Classic UI) Data views correctly synchronize with the inserted record.
  • (Touch UI) Forced notifications without text will not cause an empty alert displayed when ui.notification.enabled = false.
  • (Framework) Generated data access object has a unique name to prevent clashing with parameters created from access control rules.
  • (Framework) New property ApplicationServices.DisplayName returns application name. The value is derived either from the default app name or from the value stored in appName property in ~/touch-settings.json.
  • (Framework) Method ApplicationServices.ValidateBlobAccess ensures that user can access the row that contains the BLOB field. The field must also be accessible to the user. Otherwise access to blob is denied.
  • (Touch UI) Context menu options for child data views that were defined in their own containers are not displayed anymore. Use fields of DataView type to display child data instead. Previously visible context options have caused exceptions at runtime.
  • (Framework) Method NodeSetCollection.SetTag correctly sets tags for both data fields and views in both singular and chained calls.
  • (Touch UI) Inline editing in child data views will not cause identity fields to be marked as "Modified" and allow entering rows without errors
  • (Touch UI) Refactored panel opening and closing.
Our next goal is to release Offline Data Processor and Offline Sync in update 8.9.0.0 due out by the end of June 2019. We are skipping 8.8.0.0 release numbering since both features are being released together. Cloud On Time for Android will be out in July 2019. The new roadmap has been prepared and will be unveiled soon!


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