如何为我的iPhone应用程序保存用户首选项?

The question title pretty much gives it away - I'd like my app to remember a few things. It's some sort of calculator, so it should save the last used values and some user selectable settings.

这个问题的标题很简单——我希望我的应用能记住一些东西。它是某种计算器，所以它应该保存最后使用的值和一些用户可选择的设置。

Basically I'd like to save a handful of floats and BOOLs and load them again the next time the app loads.

基本上，我想保存一些浮点数和BOOLs，下次应用加载时再加载它们。

What's the best and easiest way to do that?

最好、最简单的方法是什么?

Thanks!!

谢谢! !

5 个解决方案

#1

One of the easiest ways would be saving it in the NSUserDefaults:

最简单的方法之一是在NSUserDefaults中保存它:

Setting:

设置:

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

[userDefaults setObject:value 
                 forKey:key];
// – setBool:forKey:
// – setFloat:forKey:  
// in your case 
[userDefaults synchronize];

Getting:

得到:

[[NSUserDefaults standardUserDefaults] objectForKey:key];

– boolForKey:

and

和

– floatForKey: in your case.

- floatForKey:对你来说。

#2

Besides the very good NSUserDefaults approach, there is another easy way to store data from an NSArray,NSDictionary or NSData in a file. You can use these methods as well:

除了非常好的NSUserDefaults方法外，还有另一种简单的方法可以将来自NSArray、NSDictionary或NSData的数据存储到文件中。你也可以使用这些方法:

- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag

respectively (for a NSDictionary):

分别(NSDictionary):

+ (id)dictionaryWithContentsOfFile:(NSString *)path

you just have to give a valid path to a location. According to the iOS Application Programming Guide, the /Library/Caches directory would be the best place to store data that you need to persist between app launches. (see here)

你只需要给一个位置一个有效的路径。根据iOS应用程序编程指南，/Library/ cache目录将是保存应用程序启动之间需要保存的数据的最佳位置。(见这里)

In order to store/load a dictionary from a filed called "managers" in your document directoy you could use these methods:

为了在文件directoy中存储/加载一个名为“managers”的文件字典，您可以使用以下方法:

-(void) loadDictionary {
    //get the documents directory:
    NSArray *paths = NSSearchPathForDirectoriesInDomains (NSCachesDirectory, NSUserDomainMask, YES);
    NSString *cacheDirectory = [paths objectAtIndex:0];
    //create a destination file name to write the data :
    NSString *fullFileName = [NSString stringWithFormat:@"%@/managers", cacheDirectory];
    NSDictionary* panelLibraryContent = [NSDictionary dictionaryWithContentsOfFile:fullFileName];
    if (panelLibraryContent != nil) {
        // load was successful do something with the data...
    } else {
        // error while loading the file
    }   
}

-(void) storeDictionary:(NSDictionary*) dictionaryToStore {
    //get the documents directory:
    NSArray *paths = NSSearchPathForDirectoriesInDomains
    (NSCachesDirectory, NSUserDomainMask, YES);
    NSString *cacheDirectory = [paths objectAtIndex:0];
    //make a file name to write the data to using the
    //cache directory:
    NSString *fullFileName = [NSString stringWithFormat:@"%@/managers", cacheDirectory];

    if (dictionaryToStore != nil) {
        [dictionaryToStore writeToFile:fullFileName atomically:YES];
    }
} 

Anyway this approach is very limited and you have to spend a lot of extra work if you want to store more complex data. In that case the CoreData API is very very handy.

无论如何，这种方法是非常有限的，如果您想存储更复杂的数据，您必须花费大量额外的工作。在这种情况下，CoreData API非常方便。

#3

In Swift:

Setting

设置

let userDefaults = NSUserDefaults.standardUserDefaults()
userDefaults.setObject(value, forKey: key)

// userDefaults.setFloat(12.34, forKey: "myFloatKey")
// userDefaults.setBool(true, forKey: "myBoolKey")

Note that for iOS 8 and later, calling userDefaults.synchronize() is not recommended.

注意，对于iOS 8和以后的版本，不建议调用userdefault .synchronize()。

Getting

得到

let userDefaults = NSUserDefaults.standardUserDefaults()
if let value = userDefaults.objectForKey(key) {
    print(value)
}

Note that userDefaults.boolForKey and userDefaults.floatForKey both return non optional values, so they would never be nil (only false or 0.0).

注意,userDefaults。boolForKey userDefaults。floatForKey都返回非可选值，因此它们永远不会是nil(只有false或0.0)。

Further reading

• NSUserDefaults — A Swift Introduction
• NSUserDefaults -快速介绍

#4

You are looking for NSUserDefaults

您正在寻找NSUserDefaults

#5

Swift 4 / Linux

斯威夫特4 / Linux

Apparently something has changed. Now there's the UserDefault class. Check these links:

显然,有些事情已经改变了。现在有了UserDefault类。检查这些链接:

https://developer.apple.com/documentation/foundation/userdefaults

https://developer.apple.com/documentation/foundation/userdefaults

https://www.hackingwithswift.com/read/12/2/reading-and-writing-basics-userdefaults

https://www.hackingwithswift.com/read/12/2/reading-and-writing-basics-userdefaults