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New example - reusing function and event definitions (#147)
Signed-off-by: Tihomir Surdilovic <[email protected]>
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‎examples/examples.md

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- [Handle Car Auction Bids (Scheduled start Event state)](#Handle-Car-Auction-Bids-Example)
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- [Check Inbox Periodically (Cron-based Workflow start)](#Check-Inbox-Periodically)
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- [Event-based service invocation (Event triggered actions)](#Event-Based-Service-Invocation)
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- [Reusing Function and Event Definitions](#Reusing-Function-And-Event-Definitions)
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### Hello World Example
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</td>
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</tr>
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</table>
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### Reusing Function And Event Definitions
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#### Description
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This example shows how [function](../specification.md#Function-Definition) and [event](../specification.md#Event-Definition) definitions
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can be declared independently and referenced by workflow definitions.
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This is useful when you would like to reuse event and function definitions across multiple workflows. In those scenarios it allows you to make
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changed/updates to these definitions in a single place without having to modify multiple workflows.
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For the example we have two files, namely our "functiondefs.json" and "eventdefs.yml" (to show that they can be expressed in either JSON or YAML).
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These hold our function and event definitions which then can be referenced by multiple workflows.
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* functiondefs.json
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```json
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{
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"functions": [
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{
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"name": "checkFundsAvailability",
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"resource": "accountFundsResource"
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},
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{
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"name": "sendSuccessEmail",
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"resource": "emailServiceResource"
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},
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{
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"name": "sendInsufficientFundsEmail",
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"resource": "emailServiceResource"
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}
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]
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}
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```
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* eventdefs.yml
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```yaml
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events:
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- name: PaymentReceivedEvent
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type: payment.receive
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source: paymentEventSource
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correlation:
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- contextAttributeName: accountId
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- name: ConfirmationCompletedEvent
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type: payment.confirmation
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kind: produced
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```
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In our workflow definition then we can reference these files rather than defining function and events in-line.
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#### Workflow Diagram
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<p align="center">
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<img src="../media/examples/example-reusefunceventdefs.png" height="400px" alt="Reusing Function and Event Definitions Example"/>
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</p>
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#### Workflow Definitions
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<table>
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<tr>
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<th>JSON</th>
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<th>YAML</th>
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</tr>
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<tr>
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<td valign="top">
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```json
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{
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"id": "paymentconfirmation",
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"version": "1.0",
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"name": "Payment Confirmation Workflow",
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"description": "Performs Payment Confirmation",
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"functions": "functiondefs.json",
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"events": "eventdefs.yml",
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"states": [
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{
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"name": "PaymentReceived",
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"type": "event",
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"onEvents": [
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{
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"eventRefs": [
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"PaymentReceivedEvent"
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],
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"actions": [
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{
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"name": "checkfunds",
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"functionRef": {
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"refName": "checkFundsAvailability",
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"parameters": {
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"account": "{{ $.accountId }}",
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"paymentamount": "{{ $.payment.amount }}"
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}
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}
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}
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]
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}
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],
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"transition": {
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"nextState": "ConfirmBasedOnFunds"
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}
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},
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{
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"name": "ConfirmBasedOnFunds",
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"type": "switch",
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"dataConditions": [
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{
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"condition": "{{ $.funds[?(@.available == 'true')] }}",
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"transition": {
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"nextState": "SendPaymentSuccess"
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}
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},
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{
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"condition": "{{ $.funds[?(@.available == 'false')] }}",
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"transition": {
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"nextState": "SendInsufficientResults"
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}
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}
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],
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"default": {
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"transition": {
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"nextState": "SendPaymentSuccess"
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}
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}
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},
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{
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"name": "SendPaymentSuccess",
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"type": "operation",
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"actions": [
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{
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"functionRef": {
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"refName": "sendSuccessEmail",
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"parameters": {
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"applicant": "{{ $.customer }}"
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}
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}
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}
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],
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"end": {
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"kind": "event",
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"produceEvents": [
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{
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"eventRef": "ConfirmationCompletedEvent",
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"data": "{{ $.payment }}"
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}
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]
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}
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},
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{
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"name": "SendInsufficientResults",
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"type": "operation",
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"actions": [
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{
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"functionRef": {
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"refName": "sendInsufficientFundsEmail",
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"parameters": {
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"applicant": "{{ $.customer }}"
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}
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}
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}
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],
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"end": {
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"kind": "event",
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"produceEvents": [
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{
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"eventRef": "ConfirmationCompletedEvent",
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"data": "{{ $.payment }}"
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}
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]
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}
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}
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]
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}
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```
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</td>
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<td valign="top">
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```yaml
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id: paymentconfirmation
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version: '1.0'
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name: Payment Confirmation Workflow
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description: Performs Payment Confirmation
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functions: functiondefs.json
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events: eventdefs.yml
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states:
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- name: PaymentReceived
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type: event
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onEvents:
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- eventRefs:
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- PaymentReceivedEvent
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actions:
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- name: checkfunds
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functionRef:
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refName: checkFundsAvailability
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parameters:
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account: "{{ $.accountId }}"
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paymentamount: "{{ $.payment.amount }}"
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transition:
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nextState: ConfirmBasedOnFunds
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- name: ConfirmBasedOnFunds
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type: switch
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dataConditions:
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- condition: "{{ $.funds[?(@.available == 'true')] }}"
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transition:
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nextState: SendPaymentSuccess
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- condition: "{{ $.funds[?(@.available == 'false')] }}"
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transition:
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nextState: SendInsufficientResults
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default:
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transition:
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nextState: SendPaymentSuccess
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- name: SendPaymentSuccess
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type: operation
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actions:
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- functionRef:
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refName: sendSuccessEmail
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parameters:
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applicant: "{{ $.customer }}"
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end:
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kind: event
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produceEvents:
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- eventRef: ConfirmationCompletedEvent
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data: "{{ $.payment }}"
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- name: SendInsufficientResults
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type: operation
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actions:
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- functionRef:
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refName: sendInsufficientFundsEmail
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parameters:
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applicant: "{{ $.customer }}"
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end:
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kind: event
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produceEvents:
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- eventRef: ConfirmationCompletedEvent
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data: "{{ $.payment }}"
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```
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</td>
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</tr>
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</table>

‎media/examples/example-reusefunceventdefs.png

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