从.txt文件读取和写入整数 [英] Read and write an integer to/from a .txt file

问题描述

如何读写文本文件中的整数，并且可以读取或写入多行，即处理多个整数？ p>感谢。

解决方案

它只是取决于文本文件的确切格式。

读取文本文件的内容很简单：

  //如果你想处理一个错误，不要将NULL传递给下面的代码，而是一个NSError指针。 
 NSString * contents = [NSString stringWithContentsOfFile：@/ path / to / fileencoding：NSUTF8StringEncoding error：NULL]; 
  

创建一个包含整个文件的自动释放字符串。如果所有的文件包含一个整数，你可以写这个：

  NSInteger integer = [contents integerValue]; 
  

如果文件分成多行（每行包含一个整数）必须将其分割：

pre $ NS $ array $ {
for（NSString * line in line）{
NSInteger currentInteger = [line integerValue];
//用整数做一些事情。



$ b $ p
$ b

总的来说，这很简单。

---

写回文件同样简单。一旦你操纵了你想要的东西回到一个字符串中，你可以使用这个：
$ b $ pre $ N $ C $ newContents = ... ; //新字符串
[newContents writeToFile：@/ path / to / fileatomically：YES encoding：NSUTF8StringEncoding error：NULL];

您可以使用它来写入字符串。当然，你可以玩设置。将自动设置为为 YES 会导致它先写入测试文件，验证它，然后复制它以替换旧文件（这可以确保如果发生故障，您不会以损坏的文件结束）。如果你愿意的话，你可以使用不同的编码（尽管强烈推荐使用 NSUTF8StringEncoding ），如果你想要发现错误（你应该从本质上来说），你可以通过对该方法的 NSError 的引用。它看起来像这样：

pre $ NSError * error = nil;
[newContents writeToFile：@someFile.txtatomically：YES encoding：NSUTF8StringEncoding error：& error];
if（error）{
//发生了一些错误。处理它。









如需进一步阅读，请参阅 NSString类参考 a>。

How can I read and write an integer to and from a text file, and is it possible to read or write to multiple lines, i.e., deal with multiple integers?

Thanks.

解决方案

This is certainly possible; it simply depends on the exact format of the text file.
Reading the contents of a text file is easy:

// If you want to handle an error, don't pass NULL to the following code, but rather an NSError pointer.
NSString *contents = [NSString stringWithContentsOfFile:@"/path/to/file" encoding:NSUTF8StringEncoding error:NULL];

That creates an autoreleased string containing the entire file. If all the file contains is an integer, you can just write this:

NSInteger integer = [contents integerValue];

If the file is split up into multiple lines (with each line containing one integer), you'll have to split it up:

NSArray *lines = [contents componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
for (NSString *line in lines) {
    NSInteger currentInteger = [line integerValue];
    // Do something with the integer.
}

Overall, it's very simple.

---

Writing back to a file is just as easy. Once you've manipulated what you wanted back into a string, you can just use this:

NSString *newContents = ...; // New string.
[newContents writeToFile:@"/path/to/file" atomically:YES encoding:NSUTF8StringEncoding error:NULL];

You can use that to write to a string. Of course, you can play with the settings. Setting atomically to YES causes it to write to a test file first, verify it, and then copy it over to replace the old file (this ensures that if some failure happens, you won't end up with a corrupt file). If you want, you can use a different encoding (though NSUTF8StringEncoding is highly recommended), and if you want to catch errors (which you should, essentially), you can pass in a reference to an NSError to the method. It would look something like this:

NSError *error = nil;
[newContents writeToFile:@"someFile.txt" atomically:YES encoding:NSUTF8StringEncoding error:&error];
if (error) {
    // Some error has occurred. Handle it.
}

---

For further reading, consult the NSString Class Reference.

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