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Questions and Answers
What is used to identify the data stored in the database for a user's vote?
What type of storage does TinyWebDB use compared to TinyDB?
What is the primary function of the TinyWebDB.GetValue block?
What happens when a TinyWebDB.GetValue request is fulfilled?
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How is the storage structure of a user's vote presented in the database?
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Which block represents the functionality of immediate value retrieval in TinyDB?
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What must be handled when using TinyWebDB to receive data?
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What is an example of a tag-value pair when a user votes for 'Pizza'?
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What is the main advantage of using a database in an app?
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What programming technique is often not taught until upper-level courses?
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Which of the following components simplifies database communication in App Inventor?
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What happens to data stored in variables and component properties when the app is closed?
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What is a common function of databases used in applications like Facebook or Amazon?
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In what scenario is the data considered persistent?
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Which database is commonly used in many programming environments for app development?
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What should happen to a user's custom message in the No Texting While Driving app once it is entered?
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What is the main purpose of the default web database?
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How does the voting app manage user votes?
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What is required from users when they enter the voting app?
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What happens if another app writes to the default web database?
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What is needed to view the votes from others in the group within the app?
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Which component is specifically mentioned as part of submitting a vote in the app?
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What aspect of TinyWebDB is highlighted in relation to the default database?
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What will users learn later in the chapter regarding web databases?
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What is the purpose of the Notifier component in the voting app?
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Why should GetValue be called after obtaining the user's email address?
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What action should be taken if the voter list received from the database is empty?
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What is the first step when the app initializes according to the logic described?
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Which component of the app checks if the data retrieved is a list?
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What should happen if the user's email is not present in the voter list?
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What does the app do after successfully retrieving the voter list?
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What condition must be met for the app to consider that it has successfully retrieved data?
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What action is taken if the user is not found in the current list?
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What happens if no voter list has been previously created?
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How are the votes submitted when a user clicks the VoteButton?
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What type of data structure is used to store the votes retrieved from the database?
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How does the application check the votes for each individual user in the voter list?
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What occurs after the app retrieves the votes from the database?
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Which of the following describes the structure of the database entries shown in the example?
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What is the intended outcome of creating a new voterList when no users have registered?
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Study Notes
Databases in App Inventor
- App Inventor simplifies database communication by offering components that make storing and retrieving data straightforward.
- Apps can store data directly on the Android device or in a centralized database on the web, allowing data sharing.
- Data stored in variables and component properties is temporary and lost when the app closes.
- Databases provide persistent data storage, meaning data remains available even after app closure.
- TinyWebDB is a web-based database service that allows App Inventor apps to share data.
- TinyWebDB.StoreValue block stores data in the web database.
- The tag identifies the data, and the value is the data itself.
- The default TinyWebDB is limited in size and accessible to all App Inventor programmers.
- It is suitable for exploration and early stages of development, but not recommended fot production apps.
Using TinyWebDB for Voting App
- The voting app utilizes TinyWebDB to store and retrieve user votes.
- Users provide their email address, which serves as the tag for their vote.
- The app retrieves and displays all votes from the database.
- TinyWebDB.GetValue requests data from the web database, but doesn't immediately return a value.
- TinyWebDB.GotValue event is triggered when data arrives from the web database.
- The app prompts the user for their email address before retrieving the voter list from the database.
- The GotValue event handler checks if the user's email is in the existing voter list.
- If the user’s email is not in the list, it is added to the voter list and stored back in the database.
- If there's no voter list yet, the user's email is added as the first item to the list.
Requesting Votes with Various Tags
- The app retrieves and displays each user's vote using a for each loop.
- The voting app utilizes a for each loop to retrieve votes for each user in the voter list.
- The loop sends a GetValue request to the database for each email address in the voter list.
- The votes are not added to the currentVotesList until they arrive through GotValue events.
Displaying Votes
- The app retrieves votes from the database using multiple GetValue requests.
- The votes are only added to the currentVotesList after they arrive through the GotValue events.
- The votes can be displayed in a visual component like a listview to showcase the voting results.
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Description
Test your knowledge on how databases are used in App Inventor, focusing on TinyWebDB and its applications, such as in a voting app. Understand the differences between temporary data storage and persistent storage options. This quiz will also cover the limitations and functionalities of TinyWebDB.