let url = URL(string: "https://api.coindesk.com/v1/bpi/currentprice.json")
let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in
if error != nil {
print ("Error!")
} else {
if let content = data {
do {
let myJson = try JSONSerialization.jsonObject(with: content) as! [String:Any]
if let rates = myJson["bpi"] as? [String:Any] {
if let currency = rates["USD"] as? [String:Any] {
if let btc = currency["rate"] as? String {
DispatchQueue.main.async{
self.bitcoinlabel.text = "$" + btc
let btcprice: Double = btc
}
}
}
}
}
catch{
print(error)
}
}
}
}
task.resume()
如何向我的ViewDidload函数添加完整的功能,以使BTCPRICE返回值BTC为值(double(而不是nil?
如@rmaddy所建议的,您无法更改ViewDidload的签名。但是,您可以做的是返回" BTCPRICE"。
只需创建一个新功能并添加到它。
func btcValue(completion: @escaping((String) -> ())){ //Added Line
let url = URL(string: "https://api.coindesk.com/v1/bpi/currentprice.json")
let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in
if error != nil {
print ("Error!")
} else {
if let content = data {
do {
let myJson = try JSONSerialization.jsonObject(with: content) as! [String:Any]
if let rates = myJson["bpi"] as? [String:Any] {
if let currency = rates["USD"] as? [String:Any] {
if let btc = currency["rate"] as? String {
DispatchQueue.main.async{
self.bitcoinlabel.text = "$" + btc
completion(btc) //Added Line
}
}
}
}
}
catch{
print(error)
}
}
}
}
task.resume()
}
}
您可以使用此代码在任何地方调用此功能。
btcValue { (btc) in
print(btc)
}
在此处阅读有关关闭的更多信息:https://developer.com/library/content/content/documentation/swift/coneptual/coneptual/swift_programming_language/closures.html