Data services
Version 1.0 - March 2017
Changelog
- Fixed outdated api to retrieve service
Introduction
One of the core steps of building a mobile application is sourcing data from different external sources. In practice, there are different options
- REST endpoints (JSON over HTTP(S) )
- MQTT endpoints (Use of MQTT messaging technology)
- SOAP endpoints
- proprietary endpoints
We describe some of the options in the following chapter
REST endpoint consumption
Consuming a REST http(s) endpoint is one of the most common scenarios. In this chapter, using the REST Service consumption wizard, we will show how to
- Consume a REST HTTPS endpoint
- Automatically parse JSON and generate Swift classes from it
- Automatically generate client Swift code to call the endpoint
- Call the REST Service and handle any kind of exception
In this example, we use a sample REST service that returns a list of dummy banking accounts. You can use it too, it's a simple REST endpoint on AWS:
https://aq5dv0hhp7.execute-api.us-west-2.amazonaws.com/prod/accounts
Executing this with username=demo and password=demo returns a JSON document
{
"username": "flangel",
"password": "12345",
"timestamp": 8923487299,
"accounts": [
{
"name": "Euro Checking",
"id": 2389233812093238,
"lastTransaction": 1417453332,
"balance": 540,
"currency": "EUR"
},
{
"name": "Rent Saving",
"id": 9032443412107340,
"lastTransaction": 1420130032,
"balance": 800,
"currency": "USD"
},
{
"name": "Frank's Checking",
"id": 9032876412119872,
"lastTransaction": 1425571626,
"balance": 1200,
"currency": "USD"
}
]
}
So lets consume the same service in our mobile app:
Step 1 - Create the data service
One data service consists of many HTTP methods, i.e. different REST endpoints that you can call. We add one GET methods first:
- Select New | Service
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- Give it a name of banking. This is name for all banking related REST endpoints
- As Request URL, specify the first REST endpoint that you want to consume
- by convention, we combine the HTTP verb with the last part of the URL
- so here, the Swift method that is generated becomes getAccounts
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- Now click on "Invoke Remote Request" to execute the request
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- Now click on Invoke Remote Request to execute the request
The username/password is demo/demo.
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- Click on Next as we will not configure request parameter
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- Review the raw contents
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- Review the model that has been generated
- Use the type column to redefine types
- Sometimes, for instance, you want to use a String type
There is no need to do anything here, just click Finish
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- Finally, press finish to create the structures
This will take 5-10 seconds. After that the Swift structures have been created that reflect this JSON structure we retrieved from the REST endpoint:
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Step 2 - Invoke the REST service
Now, all we need to do is to invoke the data service. Here a short snippet of code to invoke it.
import ScadeKit
class MainPageAdapter: SCDLatticePageAdapter {
// page adapter initialization
override func load(_ path: String) {
super.load(path)
// print name of all accounts
let accounts = getAccounts()
accounts.forEach {print($0.name)}
}
func getAccounts() -> [Accounts] {
// Get REST service reference
let bankingService: banking! = SCDRuntime.loadService("banking.service")
// Invoke service and get response
let result : AccountsResponse = bankingService.getAccounts()
// get accounts array
return result.accounts
}
}
When running it in the simulator, the accounts name are printed in the console
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Current limitations
- We don't support JSON arrays, i.e. JSON documents beginning with [ at the moment. As a workaround, parse the JSON document manually or change the JSON data structure you retrieve.
Updated almost 8 years ago