Embed Directive in Objective-C

Here’s the translation of the Go embed directive example to Objective-C, formatted in Markdown suitable for Hugo:

Objective-C doesn’t have a direct equivalent to Go’s embed directive. However, we can demonstrate how to include resource files in an Objective-C project and access them at runtime.

First, let’s create a simple Objective-C program that reads and prints the contents of a file:

#import <Foundation/Foundation.h>

@interface FileReader : NSObject
+ (NSString *)readFileWithName:(NSString *)fileName;
@end

@implementation FileReader

+ (NSString *)readFileWithName:(NSString *)fileName {
    NSString *filePath = [[NSBundle mainBundle] pathForResource:fileName ofType:nil];
    if (filePath) {
        NSError *error;
        NSString *fileContents = [NSString stringWithContentsOfFile:filePath 
                                                           encoding:NSUTF8StringEncoding 
                                                              error:&error];
        if (fileContents) {
            return fileContents;
        } else {
            NSLog(@"Error reading file: %@", error.localizedDescription);
        }
    } else {
        NSLog(@"File not found: %@", fileName);
    }
    return nil;
}

@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // Read and print the contents of single_file.txt
        NSString *singleFileContents = [FileReader readFileWithName:@"single_file.txt"];
        if (singleFileContents) {
            NSLog(@"%@", singleFileContents);
        }
        
        // Read and print the contents of file1.hash and file2.hash
        NSString *file1Contents = [FileReader readFileWithName:@"file1.hash"];
        if (file1Contents) {
            NSLog(@"%@", file1Contents);
        }
        
        NSString *file2Contents = [FileReader readFileWithName:@"file2.hash"];
        if (file2Contents) {
            NSLog(@"%@", file2Contents);
        }
    }
    return 0;
}

In this Objective-C code:

1. We define a FileReader class with a class method readFileWithName: that reads the contents of a file from the main bundle.

2. In the main function, we use this FileReader to read and print the contents of our files.

3. The NSBundle class is used to locate resources in the app bundle, which is similar to embedding files in the binary.

To use this code:

1. Create a new Objective-C command-line tool project in Xcode.

2. Replace the contents of the main.m file with the code above.

3. Add the resource files to your Xcode project:

   • Create a folder named “Resources” in your project directory.
   • Add single_file.txt, file1.hash, and file2.hash to this folder.
   • In Xcode, right-click on your project in the navigator, choose “Add Files to [YourProjectName]”, and select these files.
   • Make sure “Copy items if needed” is checked and “Add to targets” includes your main target.

4. Build and run the project in Xcode.

The output should be similar to:

hello objc
123
456

This approach doesn’t embed the files in the binary itself like Go’s embed directive, but it does include the files in the app bundle, making them accessible at runtime. This is the standard way of including and accessing resource files in Objective-C applications.

Remember that for iOS or macOS GUI applications, you would typically use NSBundle.mainBundle to access resources, as command-line tools don’t have a main bundle in the same way GUI apps do.