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TiagoBras/DispatchQueue+Extensions.swift

Created April 18, 2019 11:07
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DispatchQueue extension for situations where one needs to run an expensive operation in background and then use its result in the main thread
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DispatchQueue+Extensions.swift
import Foundation
extension DispatchQueue {
func asyncConsumeInMainQueue<T>(
work: @escaping () throws -> T,
mainSuccess: @escaping (T) -> Void,
mainError: @escaping (Error) -> Void) {
async {
do {
let result = try work()
DispatchQueue.main.async {
mainSuccess(result)
}
} catch {
DispatchQueue.main.async {
mainError(error)
}
}
}
}
func asyncConsumeInMainQueue<T>(
delay: TimeInterval,
work: @escaping () throws -> T,
mainSuccess: @escaping (T) -> Void,
mainError: @escaping (Error) -> Void) {
asyncAfter(deadline: .now() + delay) {
do {
let result = try work()
DispatchQueue.main.async {
mainSuccess(result)
}
} catch {
DispatchQueue.main.async {
mainError(error)
}
}
}
}
}
@TiagoBras
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TiagoBras commented Apr 18, 2019

Example:

DispatchQueue.global(qos: .background).asyncConsumeInMainQueue(work: { () -> UIImage in
    return try fetchImage(url: "https://example.com/image.jpeg")
}, mainSuccess: { [weak self] (image) in
    self?.imageView.image = image
}) { (error) in
    handleError(error)
}

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