Objective C - 创建文本文件，在Cocoa中逐行读写

Question

I building a Mac app,I have 2 problem:

1. I want to create a text file to read and write data on it. I don't know how to crate a text file to read and write data. Is it use struct?
2. I want to create a XML file to read and write data on it. Can I create a struct for XML?

Do you have suggestion? Thanks in advance

Answer 1

Well, to create a file, just use

[[NSFileManager defaultManager] createFileAtPath:@"Your/Path" contents:nil attributes:nil];

This creates an empty file, which you can write to or read from. To write text (or XML), just use NSString 's writeToFile:atomically:encoding:error: method like this

NSString *str = //Your text or XML
[str writeToFile:"Your/Path" atomically:YES encoding:NSUTF8StringEncoding error:nil];

To read from a file, just make an NSString with the contents of that file

NSString *contents = [NSString stringWithContentsOfFile:@"Your/Path"];

or, if it does not contain a string, get an NSData object from the file

NSData *contents = [NSData dataWithContentsOfFile:@"Your/Path"];

Answer 2

/**************************main.m******************************
    NS FILE HANDLE READ & WRITE
    reading and writing in same file
    Created by abdulsathar on 6/16/14.
***************************************************************/

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
   @autoreleasepool  //ARC
    {
        NSFileHandle *file;
        //object for File Handle
        NSError *error;
        //crearing error object for string with file contents format
        NSMutableData *writingdatatofile;
        //create mutable object for ns data
        NSString *filePath=[NSString stringWithFormat:@"/Users/chandrakumar/Documents/abdul/doc.txt"];
        //telling about File Path for Reading for easy of access
        file = [NSFileHandle fileHandleForReadingAtPath:@"/Users/chandrakumar/Documents/abdul/doc.txt"];
        //assign file path directory
            if (file == nil) //check file exist or not
                NSLog(@"Failed to open file");
        NSString *getfileContents = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
        //access file contents with out ns handle method
            if (error) //check error flag for file present or not
                NSLog(@"Error reading file: %@", error.localizedDescription);
        NSLog(@"contents: %@", getfileContents);
        //display file contents in main file
        NSArray *listArray = [getfileContents componentsSeparatedByString:@"\n"];
        //caluculate list of line present in files
        NSLog(@"items = %ld", [listArray count]);
        const char *writingchar = "how are you";
        writingdatatofile = [NSMutableData dataWithBytes:writingchar length:strlen(writingchar)];
        //convert string format into ns mutable data format
        file = [NSFileHandle fileHandleForUpdatingAtPath: @"/Users/chandrakumar/Documents/abdul/new.txt"];
        //set writing path to file
            if (file == nil) //check file present or not in file
                NSLog(@"Failed to open file");
        [file seekToFileOffset: 6];
        //object pointer initialy points the offset as 6 position in file
        [file writeData: writingdatatofile];
        //writing data to new file
        [file closeFile];
        //close the file
    }
    return 0;`enter code here`
}

/***********************************OUTPUT********************************************

 2014-06-17 14:55:39.695 storage[4075:303] contents: hello how are you my dearservice

*************************************************************************************/