Keeping a Modal with an iframe Open for 30 Seconds in Shiny

Learn how to maintain a modal dialog containing an iframe open for a specified duration in Shiny applications, and how to close it conditionally after 30 seconds.
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This video is based on the question https://stackoverflow.com/q/66033101/ asked by the user 'Frank' ( https://stackoverflow.com/u/2300622/ ) and on the answer https://stackoverflow.com/a/66033627/ provided by the user 'HubertL' ( https://stackoverflow.com/u/5038107/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Keeping a Modal with an iframe Open for 30 Seconds in Shiny

Creating dynamic user interfaces is one of the strengths of Shiny, an R package that simplifies web app development. However, developers sometimes encounter challenges, such as maintaining modals with iframes open for a specific duration and handling conditional closures. In this guide, we will uncover an effective solution to make a modal dialog containing an iframe stay open for 30 seconds and close based on certain conditions.

The Problem

Let's consider a situation where you want to open a modal dialog that includes an iframe loading a website (e.g., Google). You may want the modal to remain open for 30 seconds and then automatically close if a certain condition is met within that timeframe. Although the intention is clear, some implementations can lead to unexpected behavior or failures, especially when using blocking operations like Sys.sleep() in R.

Initial Code Blocks

Here’s the working code that successfully opens a modal with an iframe:

[[See Video to Reveal this Text or Code Snippet]]

However, if you attempt to implement a 30-second timer using a blocking loop, as shown below, it won't function as intended:

[[See Video to Reveal this Text or Code Snippet]]

As you can see, this approach may lead to unintended issues such as freezing the user interface during the waiting period. Instead, we can utilize reactive programming features in Shiny to achieve our goal more effectively.

The Solution

To keep the modal dialog open for a specified duration without freezing the UI, we can leverage the reactiveTimer() function. This allows us to create a non-blocking countdown mechanism that will periodically check if the timer has elapsed.

Updated Code

Here’s the correct implementation using reactiveTimer():

[[See Video to Reveal this Text or Code Snippet]]

How This Works

Reactive Timer: The use of reactiveTimer(1000) sets up a timer that ticks every second without blocking the app.

Observer Function: The observe() block is triggered every second, incrementing the timer (dt) and checking whether it has reached 30 seconds.

Conditional Closing: If the condition (dt >= 30) is met, the modal is closed using removeModal(). Otherwise, the timer restarts.

Conclusion

Handling modals and timers in Shiny can be daunting, but using reactiveTimer() provides a clean solution that avoids UI blocking. This allows your application to remain responsive while managing conditional logic effectively.

Feel free to modify the condition as per your application’s needs, but the foundational technique will help you maintain a modal dialog that behaves as desired! Happy coding!

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