面试题：Objective-C下网络状态变化时智能调度网络请求的策略设计

策略设计

请求队列管理：使用一个NSMutableArray来存储待执行的网络请求任务。
优先级判断：为每个请求任务添加一个优先级属性，例如使用NSInteger类型，值越大优先级越高。
网络状态监测：使用Reachability库来监测网络状态变化。
智能调度：当网络状态从无网络切换到有网络时，根据优先级从高到低依次执行请求任务，同时限制同一时间执行的请求数量，以避免网络拥塞。

关键代码实现

定义请求任务类

#import <Foundation/Foundation.h>

@interface NetworkRequest : NSObject

@property (nonatomic, strong) NSString *url;
@property (nonatomic, assign) NSInteger priority;
// 假设这里有个方法来执行实际的网络请求
- (void)executeRequest;

@end

@implementation NetworkRequest

- (void)executeRequest {
    // 实际网络请求代码，这里简单打印
    NSLog(@"Executing request for URL: %@ with priority: %ld", self.url, (long)self.priority);
}

@end

请求队列管理与优先级判断

#import <Foundation/Foundation.h>
#import "NetworkRequest.h"

@interface RequestQueueManager : NSObject

@property (nonatomic, strong) NSMutableArray<NetworkRequest *> *requestQueue;
@property (nonatomic, assign) NSInteger maxConcurrentRequests;

- (void)addRequest:(NetworkRequest *)request;
- (void)startRequests;

@end

@implementation RequestQueueManager

- (instancetype)init {
    self = [super init];
    if (self) {
        self.requestQueue = [NSMutableArray array];
        self.maxConcurrentRequests = 3; // 假设最多同时执行3个请求
    }
    return self;
}

- (void)addRequest:(NetworkRequest *)request {
    [self.requestQueue addObject:request];
}

- (void)startRequests {
    NSMutableArray<NetworkRequest *> *requestsToExecute = [NSMutableArray array];
    // 根据优先级排序，从高到低
    NSArray<NetworkRequest *> *sortedRequests = [self.requestQueue sortedArrayUsingComparator:^NSComparisonResult(NetworkRequest * _Nonnull obj1, NetworkRequest * _Nonnull obj2) {
        return obj2.priority - obj1.priority;
    }];
    for (NetworkRequest *request in sortedRequests) {
        if (requestsToExecute.count < self.maxConcurrentRequests) {
            [requestsToExecute addObject:request];
        } else {
            break;
        }
    }
    for (NetworkRequest *request in requestsToExecute) {
        [request executeRequest];
        // 实际应用中这里应该是异步执行请求，并在请求完成后从队列中移除
        [self.requestQueue removeObject:request];
    }
    // 递归执行剩余请求
    if (self.requestQueue.count > 0) {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [self startRequests];
        });
    }
}

@end

网络状态监测与调度触发

#import "ViewController.h"
#import <AFNetworking/AFNetworking.h>
#import "RequestQueueManager.h"

@interface ViewController ()

@property (nonatomic, strong) RequestQueueManager *queueManager;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.queueManager = [[RequestQueueManager alloc] init];
    
    // 监测网络状态
    AFNetworkReachabilityManager *reachabilityManager = [AFNetworkReachabilityManager sharedManager];
    [reachabilityManager startMonitoring];
    [reachabilityManager setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
        if (status == AFNetworkReachabilityStatusReachableViaWiFi || status == AFNetworkReachabilityStatusReachableViaWWAN) {
            [self.queueManager startRequests];
        }
    }];
    
    // 添加一些示例请求
    NetworkRequest *request1 = [[NetworkRequest alloc] init];
    request1.url = @"https://example.com/api1";
    request1.priority = 2;
    [self.queueManager addRequest:request1];
    
    NetworkRequest *request2 = [[NetworkRequest alloc] init];
    request2.url = @"https://example.com/api2";
    request2.priority = 1;
    [self.queueManager addRequest:request2];
    
    NetworkRequest *request3 = [[NetworkRequest alloc] init];
    request3.url = @"https://example.com/api3";
    request3.priority = 3;
    [self.queueManager addRequest:request3];
}

@end

以上代码实现了一个简单的网络请求队列管理和优先级调度系统，在网络状态恢复时，能够智能调度请求任务并避免网络拥塞。实际应用中，网络请求部分可能需要使用更成熟的网络框架（如AFNetworking或Alamofire），并且在请求完成后需要正确处理队列的更新。

面试题：Objective-C下网络状态变化时智能调度网络请求的策略设计

知识考点

面试题答案

策略设计

关键代码实现