History Management

Lesson 6 - Custom statehash

This lesson will demonstrate how to change and use the custom StateHash. Just to recap - a StateHash consists of the viewname, followed by the recordid, followed by some optional custom data. This last bit is the custom StateHash. When used correctly, it can be a very powerful and flexible tool.

To set a custom StateHash, the procedure ‘OnDefineCustomStateHash’ is augmented. The StateHash is passed as a byref parameter, so it only needs to be altered inside the procedure itself. To get the custom StateHash, call on Get CustomStateHash and store it in a string variable.

Finally, to manually force an update, use Send UpdateStateHash. Pass along true if the current history item is to be replaced, or false if a new one is to be added to the stack. Calling on this procedure also loops through OnDefineCustomStateHash.

DEMONSTRATION

The example view, oVwPersonZoom, contains a form called Custom Text.
Two things need to happen to change and use the a custom StateHash:
1. Whenever the value of the CustomText form is changed, the value needs to be reflected in the StateHash
2. Whenever the view is entered via a direct URL, the form needs to be populated with the value of the custom StateHash
The first step for the first item is to set pbServerOnChange for the form to true in the Properties Panel.
Next, implement the OnChange procedure. Inside this procedure, call on UpdateStateHash, and pass along true since the current StateHash is to be replaced with the updated one.
Next, implement the OnDefineCustomStateHash in the view. The goal is to take the value of our CustomText form and update our StateHash with it. Note that the StateHash is passed as a byref parameter, so that needs to be set.
Add WebGet psValue of oWfCustomText to sStateHash.
Step one is now complete.
For step two, set pbServerOnShow for the view to True in the Properties Panel.
Next, implement the OnShow procedure. To do so, a string variable, sCustomerHash, is set. Then add Get CustomStateHash to sCustomHash. Then WebSet psValue of oWfCustomText to sCustomHash. Finally call on UpdateStateHash again to reflect everything.
After compiling and running the application, the PersonZoom view shows the custom text form. When “Hello” is entered in the form, the StateHash is updated with the value just entered.
Conversely, if we replace “Hello” with “Goodbye” in the URL, the value in the form is updated.

History Management

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History Management

Lesson 6 - Custom statehash