Directories in Objective-C

Here’s the translation of the Go code to Objective-C, with explanations in Markdown format suitable for Hugo:

Our first program will demonstrate working with directories in Objective-C. Here’s the full source code:

#import <Foundation/Foundation.h>

@interface DirectoryManager : NSObject
+ (void)createEmptyFileAtPath:(NSString *)path;
+ (void)check:(NSError *)error;
+ (void)visitPath:(NSString *)path;
@end

@implementation DirectoryManager

+ (void)createEmptyFileAtPath:(NSString *)path {
    NSData *emptyData = [NSData data];
    NSError *error;
    [emptyData writeToFile:path options:NSDataWritingAtomic error:&error];
    [self check:error];
}

+ (void)check:(NSError *)error {
    if (error) {
        @throw [NSException exceptionWithName:NSGenericException reason:[error localizedDescription] userInfo:nil];
    }
}

+ (void)visitPath:(NSString *)path {
    BOOL isDirectory;
    [[NSFileManager defaultManager] fileExistsAtPath:path isDirectory:&isDirectory];
    NSLog(@" %@, isDirectory: %d", path, isDirectory);
}

@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSError *error;
        NSFileManager *fileManager = [NSFileManager defaultManager];
        
        // Create a new sub-directory in the current working directory
        [fileManager createDirectoryAtPath:@"subdir" withIntermediateDirectories:NO attributes:nil error:&error];
        [DirectoryManager check:error];
        
        // Create empty files
        [DirectoryManager createEmptyFileAtPath:@"subdir/file1"];
        
        // Create a hierarchy of directories
        [fileManager createDirectoryAtPath:@"subdir/parent/child" withIntermediateDirectories:YES attributes:nil error:&error];
        [DirectoryManager check:error];
        
        [DirectoryManager createEmptyFileAtPath:@"subdir/parent/file2"];
        [DirectoryManager createEmptyFileAtPath:@"subdir/parent/file3"];
        [DirectoryManager createEmptyFileAtPath:@"subdir/parent/child/file4"];
        
        // List directory contents
        NSArray *contents = [fileManager contentsOfDirectoryAtPath:@"subdir/parent" error:&error];
        [DirectoryManager check:error];
        
        NSLog(@"Listing subdir/parent");
        for (NSString *item in contents) {
            BOOL isDirectory;
            [fileManager fileExistsAtPath:[@"subdir/parent" stringByAppendingPathComponent:item] isDirectory:&isDirectory];
            NSLog(@" %@, isDirectory: %d", item, isDirectory);
        }
        
        // Change directory
        [fileManager changeCurrentDirectoryPath:@"subdir/parent/child"];
        
        contents = [fileManager contentsOfDirectoryAtPath:@"." error:&error];
        [DirectoryManager check:error];
        
        NSLog(@"Listing subdir/parent/child");
        for (NSString *item in contents) {
            BOOL isDirectory;
            [fileManager fileExistsAtPath:item isDirectory:&isDirectory];
            NSLog(@" %@, isDirectory: %d", item, isDirectory);
        }
        
        // Change back to original directory
        [fileManager changeCurrentDirectoryPath:@"../../.."];
        
        // Walk directory recursively
        NSLog(@"Visiting subdir");
        NSDirectoryEnumerator *enumerator = [fileManager enumeratorAtPath:@"subdir"];
        NSString *path;
        while ((path = [enumerator nextObject])) {
            [DirectoryManager visitPath:[NSString stringWithFormat:@"subdir/%@", path]];
        }
        
        // Clean up
        [fileManager removeItemAtPath:@"subdir" error:&error];
        [DirectoryManager check:error];
    }
    return 0;
}

This program demonstrates various operations with directories in Objective-C:

We create a new sub-directory using createDirectoryAtPath:withIntermediateDirectories:attributes:error:.
We use a helper method createEmptyFileAtPath: to create empty files.
We create a hierarchy of directories using createDirectoryAtPath:withIntermediateDirectories:attributes:error: with the withIntermediateDirectories flag set to YES.
We list directory contents using contentsOfDirectoryAtPath:error:.
We change the current working directory using changeCurrentDirectoryPath:.
We walk a directory recursively using NSDirectoryEnumerator.
Finally, we clean up by removing the created directory structure.

To run the program, compile it and then execute the resulting binary:

$ clang -framework Foundation directories.m -o directories
$ ./directories
Listing subdir/parent
 child, isDirectory: 1
 file2, isDirectory: 0
 file3, isDirectory: 0
Listing subdir/parent/child
 file4, isDirectory: 0
Visiting subdir
 subdir, isDirectory: 1
 subdir/file1, isDirectory: 0
 subdir/parent, isDirectory: 1
 subdir/parent/child, isDirectory: 1
 subdir/parent/child/file4, isDirectory: 0
 subdir/parent/file2, isDirectory: 0
 subdir/parent/file3, isDirectory: 0

This example demonstrates how to work with directories in Objective-C, including creating, listing, and traversing directory structures.

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Directories in Objective-C