[iOS] Swift: How to store user preferences?

Apple 官方教學：
https://developer.apple.com/documentation/foundation/userdefaults

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You can use NSUserDefaults to save information and retrieve it next time when the app launches.

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/index.html

For Save example:

UserDefaults.standard.setValue(UserId, forKey: "UserId")

 

For Load example:

let tmpUserId = UserDefaults.standard.string(forKey: "UserId")
if (tmpUserId != nil) {
 UserId = tmpUserId!
}

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Use NSUserDefaults

Let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject("User", forKey: "userName")

Check if User name exists when application is started in your AppDelegate.swift

didFinishLaunchingWithOptions

If username exists, skip login page

To check if NSUserDefaults is nil

if (defaults.objectForKey(userName) != nil) { 
// Skip Login 
}
else {// Show login 
} 

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Objective-C 版本：

Save：

NSString *valueToSave = @"someValue";
[[NSUserDefaults standardUserDefaults] setObject:valueToSave forKey:@"preferenceName"];
[[NSUserDefaults standardUserDefaults] synchronize];

to get it back later：

NSString *savedValue = [[NSUserDefaults standardUserDefaults]
    stringForKey:@"preferenceName"];

 

 

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這個範例有點特別，如果是 self sign 的話，可以會跑進這一個 method:

– (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential))completionHandler

 

如果是合法的 sign 的話，只會跑進下面的不會跑上面的；

如果是 self sign 上面/下面都會執行，結論，是使用下面這組：

-(void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler {