operation.md

Operations

This topic will show how to manually deserialize an operation. If you want to learn the automatic and recommended approach (code generation), please read the topic "Operation" instead.

We'll use the same operation implemented here.

You'll implement the operation just like the automatic version, but without the annotation @AutoDeserialize.

Register the operation

For manual deserialization, we need to use the list of arguments passed to the operation. This list of arguments is provided as the single parameter of the function used to register the operation. See the example below:

val myAppUI = NimbusComposeUILibrary("myApp")
    .addOperation("formatCurrency") { 
        val value = it[0] as Double // first argument passed to the operation
        val currency = it[1] as String // second argument passed to the operation
        return formatCurrency(value, currency)
    },
)

Whenever the operation "formatCurrency(x, y)" is used by an expression of a server driven view, the function formatCurrency will be called with a list where the first position corresponds to x and second to y.

The code above is just an example, it is still unsafe since we're not always checking if the value is of the type we expect before casting it. We also have no treatment for when the expected properties are not available. To help with this, Nimbus provides the class AnyServerDrivenData, see below an example of how to use it:

val myAppUI = NimbusComposeUILibrary("myApp")
    .addOperation("formatCurrency") {
        val data = AnyServerDrivenData(it)
        val value = data.at(0).asDouble() // first argument passed to the operation
        val currency = data.at(1).asString() // second argument passed to the operation
        if (data.hasError()) throw IllegalArgumentException(data.errorsAsString())
        return formatCurrency(value, currency)
    },
)

AnyServerDrivenData will collect the deserialization errors if they happen, without stopping the execution. It also makes automatic type coercions for helping with type management. If you are going to use manual deserialization, we highly recommend the use of this class.

If we find any deserialization error, instead of calling the operation, we throw an exception, which will be treated and printed as an error log by Nimbus.

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