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Lines and polygons are not captured until the user has moved a minimum distance from the first vertex. Lines require a minimum of two vertices, and polygons require a minimum of three vertices.

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A project can be configured to accept input from the user. The user can enter the input before or after a button is pressed. The project author defines the buttons and fields to which the value is applied.

Rarely, you may want to execute code which may read signals within a reactive function such as computed or effect without creating a dependency.

Effects might start long-running operations, which you should cancel if the effect is destroyed or runs again before the first operation finished. When you create an effect, your function can optionally accept an onCleanup function as its first parameter. This onCleanup function lets you register a callback that is invoked before the next run of the effect begins, or when the effect is destroyed.

Only the signals actually read during the derivation are tracked. For example, in this computed the count signal is only read if the showCount signal is true:

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This example will log a message when either currentUser or counter changes. However, if the effect should only run when currentUser changes, then the read of counter is only incidental and changes to counter shouldn't log a new message.

When you read conditionalCount, if showCount is false the "Nothing to see here!" message is returned without reading the count signal. This means that if you later update count it will not result in a recomputation of conditionalCount.

User input is configured by the project author and can be typed with a keyboard, selected from a list, or scanned from a barcode.

If you then change count, Angular knows that doubleCount's cached value is no longer valid, and the next time you read doubleCount its new value will be calculated.

An exclusivity group is used to ensure that only one button in the group is active at any time. The project author can include buttons from different template groups in a single exclusivity group, and multiple exclusivity groups can be applied to a project.

By default, you can only create an effect() within an injection context (where you have access to the inject function). The easiest way to satisfy this requirement is to call effect within a component, directive, or service constructor:

While your device is online, your captured records are automatically sent. If your device is offline, your captured records are automatically sent the next time you're online.

When you close a project by returning to the project gallery, the following happens:Any active line, polygon, or streaming point capture ends and is saved.If you are online, all data is sent.If you are offline, all data is saved on the device.

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When you read a signal within an OnPush component's template, Angular tracks the signal as a dependency of that component. When the value of that signal changes, Angular automatically marks the component to ensure it gets updated the next time change detection runs. Refer to the Skipping component subtrees guide for more information about OnPush components.

The horizontal accuracy error only stops the user from pressing the button to start capturing lines, polygons, or streaming points. Once active, line and polygon vertices with an accuracy below the threshold are excluded from the captured geometry. Conversely, all streaming points are captured, even if they don't meet the accuracy threshold.

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If you do not have an ArcGIS account, you can still use QuickCapture. Select Continue without signing in on the sign-in page to download and use one of the sample projects.

Writable signals provide an API for updating their values directly. You create writable signals by calling the signal function with the signal's initial value:

The doubleCount signal depends on the count signal. Whenever count updates, Angular knows that doubleCount needs to update as well.

Computed signal are read-only signals that derive their value from other signals. You define computed signals using the computed function and specifying a derivation:

Angular Signals is a system that granularly tracks how and where your state is used throughout an application, allowing the framework to optimize rendering updates.

A signal is a wrapper around a value that notifies interested consumers when that value changes. Signals can contain any value, from primitives to complex data structures.

Effects always run at least once. When an effect runs, it tracks any signal value reads. Whenever any of these signal values change, the effect runs again. Similar to computed signals, effects keep track of their dependencies dynamically, and only track signals which were read in the most recent execution.

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A project can also be configured with a required horizontal accuracy. If so, the user cannot capture a record until the accuracy threshold has been met.

As a result, you can safely perform computationally expensive derivations in computed signals, such as filtering arrays.

If a button is used to launch a URL, it does not capture a record, but instead opens the URL with the default browser on your device. You can configure the button to pass predefined values along with the URL as parameters. For more information, see Integrate with other apps.

Effects return an EffectRef that you can use to destroy them manually, by calling the .destroy() method. You can combine this with the manualCleanup option to create an effect that lasts until it is manually destroyed. Be careful to actually clean up such effects when they're no longer required.

If you set showCount to true and then read conditionalCount again, the derivation will re-execute and take the branch where showCount is true, returning the message which shows the value of count. Changing count will then invalidate conditionalCount's cached value.

QuickCapture uses the predictive text capabilities of the device for user input. When entering a single word on Android, you must select the word from the recommended options or enter a space after the single word to be able to select Done. On iOS, you can immediately close the keyboard and select Done.

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When creating a signal, you can optionally provide an equality function, which will be used to check whether the new value is actually different than the previous one.

If enabled and supported by your device, tapping a button gives an audio response (text to speech or beep) and haptic feedback to provide confirmation that the button has been pressed.

Effects are rarely needed in most application code, but may be useful in specific circumstances. Here are some examples of situations where an effect might be a good solution:

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When you create an effect, it is automatically destroyed when its enclosing context is destroyed. This means that effects created within components are destroyed when the component is destroyed. The same goes for effects within directives, services, etc.

doubleCount's derivation function does not run to calculate its value until the first time you read doubleCount. The calculated value is then cached, and if you read doubleCount again, it will return the cached value without recalculating.

ArcGIS QuickCapture is a field data capture app that allows you to capture data quickly. You can capture both the location and attributes of assets or incidents as you travel. A project author determines the arrangement of buttons, how they appear, and the information they collect. The app allows you to capture photos, video, and sensor information from the device.

Signals are useful because they notify interested consumers when they change. An effect is an operation that runs whenever one or more signal values change. You can create an effect with the effect function:

Avoid using effects for propagation of state changes. This can result in ExpressionChangedAfterItHasBeenChecked errors, infinite circular updates, or unnecessary change detection cycles.

For example, suppose that when currentUser changes, the value of a counter should be logged. you could create an effect which reads both signals:

If the project was configured to request a user input after a button is pressed, enter a valid value before pressing another button.

A project can be configured to require or optionally enable location sharing. If your project requires location sharing, it cannot be disabled in the mobile app. If it is optional, you can turn off location sharing.

If the project is not already on your device, the download icon changes to an information icon once the download is complete. If you do not see projects to download, contact your project administrator and ask for the project to be shared with you.

Optionally, a project can be configured to use an exclusivity group. In this case, tapping a button can stop the capture of one feature and start capturing the next one.

Note that dependencies can be removed during a derivation as well as added. If you later set showCount back to false, then count will no longer be considered a dependency of conditionalCount.