nslog可以打印变量，但变量不保持值？

Question

I have this:

    NSUserDefaults *defauts = [NSUserDefaults standardUserDefaults];
    NSString *namestr = [defauts objectForKey:@"savednamestring"];

    NSLog(@"%@",namestr);
    [unusedtext setText:namestr];
    NSLog(@"%@",unusedtext); 
    NSLog(@"%@",unusedtext.text);

Now, first nslog prints out the content of namestr , for instance "Jack".

But the second nslog and 3rd nslog both give null .

when i try to pass namestr into entity it gives me an unrecognized selector sent to instance error, and i know it is because of namestr not passing anything into the entity, but how nslog print out namestr at the first place. And do i need to convert it into some sort of format to make it work?

Answer 1

unusedText可能未初始化。

Answer 2

I'm assuming that the unusedtext is an UILabel.

There are a few questions:

• Are you using Interface Builder or Storyboard? If yes, did you linked the var with the component?
• If you are not using IB or Storyboard, is this "unusedtext" initialized?
• Are you using ARC? If no, isn't the unusedtext autorelease? Or released before your code?
• If you are using ARC, is the unusedtext marked as STRONG?

Hope to help!

Answer 3

thats because you haven't initialized unusedtext variable.

if it is NSString then do this

NSUserDefaults *defauts = [NSUserDefaults standardUserDefaults];
NSString *namestr = [defauts objectForKey:@"savednamestring"];

NSLog(@"%@",namestr);
unusedtext = [NSString stringWithString:namestr];
NSLog(@"%@",unusedtext); 
NSLog(@"%@",unusedtext.text);

and if it is a UITextView or UITextfield than do this, instead!

NSUserDefaults *defauts = [NSUserDefaults standardUserDefaults];
NSString *namestr = [defauts objectForKey:@"savednamestring"];

NSLog(@"%@",namestr);
UITextField *unusedtext = [[UITextField alloc] init];
[unusedtext setText:namestr];
NSLog(@"%@",unusedtext); 
NSLog(@"%@",unusedtext.text);

hope that helps!