将字符串保存到NSUserDefaults？

Question

如何将字符串保存到NSUserDefaults？

Answer 1

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

以后再拿回来

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

Answer 2

更确切地说

-(void)saveToUserDefaults:(NSString*)myString
{
    NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];

    if (standardUserDefaults) {
        [standardUserDefaults setObject:myString forKey:@"timestamps"];
        [standardUserDefaults synchronize];
    }
}

Answer 3

以下是Swift的相同操作方法;

var valueToSave = "someValue"
NSUserDefaults.standardUserDefaults().setObject(valueToSave, forKey: "preferenceName")

以后再回来;

if let savedValue = NSUserDefaults.standardUserDefaults().stringForKey("preferenceName") {
    // Do something with savedValue
}

在Swift 3.0中

var valueToSave = "someValue"
UserDefaults.standard.set(valueToSave, forKey: "preferenceName")

if let savedValue = UserDefaults.standard.string(forKey: "preferenceName") {

}

Answer 4

像这样的东西:

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

// saving an NSString
[prefs setObject:@"TextToSave" forKey:@"keyToLookupString"];

然后检索:

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

// getting an NSString
NSString *myString = [prefs stringForKey:@"keyToLookupString"];

您应该查看Apple的NSUserDefaults类参考,​​也可以查看本教程:iPhone编程教程 - 使用NSUserDefaults保存/检索数据

Answer 5

不要忘记这句话,否则它可能并不总是有效:

[standardUserDefaults synchronize];

Answer 6

[[NSUserDefaults standardUserDefaults] setValue:aString forKey:aKey]

Answer 7

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

// saving an NSString
[prefs setObject:@"TextToSave" forKey:@"keyToLookupString"];

// saving an NSInteger
[prefs setInteger:42 forKey:@"integerKey"];

// saving a Double
[prefs setDouble:3.1415 forKey:@"doubleKey"];

// saving a Float
[prefs setFloat:1.2345678 forKey:@"floatKey"];

// This is suggested to synch prefs, but is not needed (I didn't put it in my tut)
[prefs synchronize];

检索

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

// getting an NSString
NSString *myString = [prefs stringForKey:@"keyToLookupString"];

// getting an NSInteger
NSInteger myInt = [prefs integerForKey:@"integerKey"];

// getting an Float
float myFloat = [prefs floatForKey:@"floatKey"];

Answer 8

一个好的做法是使用密钥的常量来避免不使用相同密钥存储和读取的错误

NSString* const TIME_STAMPS_KEY = @"TIME_STAMPS_KEY";