BHDownload.h

@protocol BHDownloadDelegate <NSObject>
- (void)downloadProgress:(float)progress;
- (void)downloadDidFinish:(NSURL *_Nullable)filePath Filename:(NSString *_Nullable)fileName;
- (void)downloadDidFailureWithError:(NSError *)error;
@end

@interface BHDownload : NSObject
{
   id delegate;
}
- (void)setDelegate:(id _Nonnull )newDelegate;
- (instancetype _Nullable )init;
- (void)downloadFileWithURL:(NSURL *_Nullable)url;
@property (nonatomic, strong) NSString * _Nullable fileName;
@end

@interface BHDownload () <NSURLSessionDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate, NSURLSessionStreamDelegate>
@property (nonatomic, strong) NSURLSession * _Nullable Session;
@end

BHDownload.m

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import "BHDownload.h"

@implementation BHDownload

- (instancetype _Nullable )init {
    self = [super init];
    if (self) {
        self.Session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    }
    return self;
}

- (void)downloadFileWithURL:(NSURL *_Nullable)url {
    if (url) {
        self.fileName = url.absoluteString.lastPathComponent;
        NSURLSessionDownloadTask *downloadTask = [self.Session downloadTaskWithURL:url];
        [downloadTask resume];
    }
}
- (void)setDelegate:(id _Nonnull )newDelegate {
    if (newDelegate) {
        delegate = newDelegate;
    }
}
- (void)URLSession:(nonnull NSURLSession *)session downloadTask:(nonnull NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
    float prog = (float)totalBytesWritten / (float)totalBytesExpectedToWrite;
    [delegate downloadProgress:prog];
}
- (void)URLSession:(nonnull NSURLSession *)session downloadTask:(nonnull NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(nonnull NSURL *)location {
    [delegate downloadDidFinish:location Filename:self.fileName];
}
- (void)URLSession:(nonnull NSURLSession *)session didBecomeInvalidWithError:(NSError *)error {
    [delegate downloadDidFailureWithError:error];
}
- (void)URLSession:(nonnull NSURLSession *)session task:(nonnull NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
    [delegate downloadDidFailureWithError:error];
}
@end

Example.m

@interface ViewController () <BHDownloadDelegate>

@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    BHDownload *download = [[BHDownload alloc] init];
    [download setDelegate:self];
    [download downloadFileWithURL:[NSURL URLWithString:@"http://ipv4.download.thinkbroadband.com/5MB.zip"]];
}
- (void)downloadProgress:(float)progress {
    NSLog(@"%f", progress);
}

- (void)downloadDidFinish:(NSURL *)filePath Filename:(NSString *)fileName {
    NSLog(@"%@\n%@", filePath, fileName);
}
- (void)downloadDidFailureWithError:(NSError *)error {
    NSLog(@"error123: %@", error.description);
}
@end