Suraj Kumar Mandal

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How to Do Multiple API Calls Simultaneously in Swift iOS

mapkit in swift

When developing an iOS app, it’s common to need to make multiple API calls to fetch different sets of data. However, making these calls one after another can slow down your app’s performance and make it feel unresponsive to the user. In this blog post, we will explore how to do multiple API calls simultaneously in Swift iOS, improving the efficiency and responsiveness of your app.

1. Using DispatchGroup

One way to make multiple API calls simultaneously is by using the DispatchGroup class provided by the Grand Central Dispatch (GCD) framework. DispatchGroup allows you to group multiple tasks together and wait for them to complete before proceeding.

Here’s an example of how to use DispatchGroup to make multiple API calls:

let dispatchGroup = DispatchGroup()

dispatchGroup.enter()
APIManager.fetchData1 { result in
  // Process the result of the first API call
 dispatchGroup.leave()
}
dispatchGroup.enter()
APIManager.fetchData2 { result in
 // Process the result of the second API call
 dispatchGroup.leave()
}
dispatchGroup.enter()
APIManager.fetchData3 { result in
 // Process the result of the third API call
 dispatchGroup.leave()
}
dispatchGroup.notify(queue: .main) {
 // All API calls have completed
 // Update the UI or perform any other tasks
}

In this example, we create a DispatchGroup instance and enter the group before each API call. After each API call is completed, we leave the group. Finally, we use the notify(queue:) method to specify a closure that will be executed when all API calls have completed.

2. Using OperationQueue

Another approach to making multiple API calls simultaneously is by using the OperationQueue class. OperationQueue allows you to add multiple operations to a queue and execute them concurrently.

Here’s an example of how to use OperationQueue to make multiple API calls:

let operationQueue = OperationQueue()

let operation1 = BlockOperation {
 APIManager.fetchData1 { result in
  // Process the result of the first API call
 }
}
let operation2 = BlockOperation {
 APIManager.fetchData2 { result in
  // Process the result of the second API call
 }
}
let operation3 = BlockOperation {
 APIManager.fetchData3 { result in
  // Process the result of the third API call
 }
}

operationQueue.addOperations([operation1, operation2, operation3], waitUntilFinished: true)
// All API calls have completed
// Update the UI or perform any other tasks

In this example, we create an OperationQueue instance and add multiple operations to the queue. Each operation represents an API call, and we specify the code to be executed for each API call in a closure. Finally, we use the waitUntilFinished parameter to wait for all operations to complete before proceeding.

3. Using URLSession

If you prefer a more low-level approach, you can use URLSession to make multiple API calls simultaneously. URLSession provides a way to create and manage multiple URLSessionDataTask objects, each representing an API call.

Here’s an example of how to use URLSession to make multiple API calls:

let session = URLSession.shared
let url1 = URL(string: "https://api.example.com/data1")!
let url2 = URL(string: "https://api.example.com/data2")!
let url3 = URL(string: "https://api.example.com/data3")!
let task1 = session.dataTask(with: url1) { data, response, error in
 // Process the result of the first API call
}
let task2 = session.dataTask(with: url2) { data, response, error in
 // Process the result of the second API call
}
let task3 = session.dataTask(with: url3) { data, response, error in
 // Process the result of the third API call
}
task1.resume()
task2.resume()
task3.resume()
// All API calls have been started
// Update the UI or perform any other tasks

In this example, we create a URLSession instance and define the URLs for the API calls. We then create URLSessionDataTask objects for each API call and specify the code to be executed when the data task is completed. Finally, we call the resume() method on each data task to start the API calls.

Conclusion

Making multiple API calls simultaneously can significantly improve the performance and responsiveness of your iOS app. In this blog post, we explored three different approaches to achieve this: using DispatchGroup, using OperationQueue, and using URLSession. Each approach has its own advantages and may be more suitable for different scenarios.

By implementing these techniques in your iOS app, you can ensure that your app remains fast and efficient, providing a seamless user experience even when dealing with multiple API calls.

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