NSNumber和浮动？

Question

I am trying to set an NSNumber as a float value that has been loaded using NSUserDefaults but i'm getting an error. I can't understand why...?

Here's my code:

[settingsData.sensitivitySettingValue floatValue] = [[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"];

It works if I use a float on its own (ie float myFloat = [[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"]

, but I want the value available across all view controllers so I have defined it in a model class as an NSNumber.

So, please would anyone be able to advise me on why that statement wont work?

Answer 1

That looks like you're trying to assign a variable to a getter method, judging by your syntax. What does floatValue do? Return a value or assign one?

Answer 2

taking settingsData as an object of your datamodel class where sensitivitySettingValue is a variable declared as NSNumber using something as

[settingsData.sensitivitySettingValue floatValue]

actually fetches its value rather than setting a float value to it . You can either use the dot notation such as settingsData.sensitivitySettingValue = [NSNumber numberWithFloat:[[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"]];

or something as

[settingsData setSensitivitySettingValue:[NSNumber numberWithFloat:[[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"]]];

Hope it helps

Answer 3

You can try

+ (NSNumber *)numberWithFloat:(float)value;

method to assign the value. Here is the Docs .

Answer 4

[settingsData.sensitivitySettingValue setFloatValue:[[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"]];

确保settingsData.sensitivitySettingValue支持setFloatValue方法。

Answer 5

If you want to create NSNumber from float:

float myFloat = [[NSUserDefaults standardUserDefaults] floatForKey:@"sensitivityKey"];
NSNumber *number = [NSNumber numberWithFloat:myFloat];
// settingsData.sensitivitySettingValue = number; - not sure in type of properties

NSUserDefaults also responds to objectForKey method, you can save/load NSNumber without casting