需求描述：
项目用户认证功能更新证件图片，并且证件图片分三组，每一组最多可以上传三张图片，因为是更新功能，所以每一组图片中，可能存在原来的图片(是url链接字符串)，还有可能是重新选择的图片如相册或着拍摄获取(是UIImage格式).
后台提供的接口是一次上传一组照片，照片以base64转码的方式上传
结构
创建异步并发队列，并且使用队列组监听全部任务执行完成，返回最终结果
// 最大并发
#define MaxRequests 3
#pragma mark - private Method
/// 上传多组图片(支持UIImage或url字符串混合)
/// @param dataArray 内部也是一组数组
/// @param success success
/// @param failure failure
- (void)uploadPhotosWithDataArray:(NSArray <NSArray *>*)dataArray
success:(void(^)(NSArray *result))success
failure:(void(^)(NSString *msg))failure {
/*
dataArray的数据可能是url字符串 或者 UIImage类型
如果是url字符串则不上传
如果是UIImage则上传
*/
// 存储最终结果
__block NSMutableArray *result = [NSMutableArray arrayWithArray:dataArray];
// 创建并发队列
dispatch_queue_t queue = dispatch_queue_create("uploadPhoto_queue",DISPATCH_QUEUE_CONCURRENT);
// 创建队列组
dispatch_group_t group = dispatch_group_create();
// 设置最大并发量
dispatch_semaphore_t semaphore = dispatch_semaphore_create(MaxRequests);
for (int i=0; i<dataArray.count; i++) {
// 将每个数组中的UIImage对象转为base64格式
dispatch_group_async(group, queue, ^{
// 等待降低信号量
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
NSArray *row = [result objectAtIndex:i];
NSString *mainDomain = [NSString stringWithFormat:@"https://%@",Domain];
NSMutableArray *tempArr = [NSMutableArray arrayWithArray:row];
NSMutableArray *needUploadArr = [NSMutableArray array];
NSMutableArray *needUploadIndex = [NSMutableArray array];
for (int j=0; j<row.count; j++) {
NSString *url = [row objectAtIndex:j];
// 如果原来的url链接字符串中有域名还需要将域名清空
if ([url isKindOfClass:NSString.class]) {
if ([url hasPrefix:mainDomain]) {
NSString *newUrl = [url stringByReplacingOccurrencesOfString:mainDomain withString:@""];
[tempArr replaceObjectAtIndex:j withObject:newUrl];
}
}
else if ([url isKindOfClass:UIImage.class]) {
NSString *base64String = [LYClassUtils imageToBase64Str:(UIImage *)url maxLength:50];
[needUploadArr addObject:base64String];
[needUploadIndex addObject:@(j)];
}
}
[result replaceObjectAtIndex:i withObject:tempArr];
// 请求数据
if (needUploadArr.count > 0) {
// 网络请求模块
[LYNetworkManager uploadImagesWithArray:needUploadArr success:^(id responseObject) {
LYBaseResultModel *responeResult = [LYBaseResultModel mj_objectWithKeyValues:responseObject];
// 上传成功，将原来的UIImage替换成url字符串
if (responeResult.isSuccess) {
NSDictionary *content = [responseObject objectForKey:@"content"];
NSArray *imgs = [content objectForKey:@"headImgArray"];
for (int k=0; k<needUploadIndex.count; k++) {
NSNumber *tempIndex = needUploadIndex[k];
[tempArr replaceObjectAtIndex:tempIndex.integerValue withObject:imgs[k]];
}
[result replaceObjectAtIndex:i withObject:tempArr];
}else{
failure(responeResult.message);
}
// 请求完成执行：发送信号,继续请求
dispatch_semaphore_signal(semaphore);
} failure:^(NSError *error) {
// 请求完成执行：发送信号
dispatch_semaphore_signal(semaphore);
}];
}
else{
// 不需要上传：发送信号,继续请求
dispatch_semaphore_signal(semaphore);
}
});
}
// 监听任务组，如果执行完成，则返回最终结果
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
success(result);
});
}
问题点
异步网络还未执行完成，就已经返回最终的结果,dispatch_group_notify方法回调
分析
导致这个结果可能是因为：并发队列是异步执行的，异步执行的任务中又是网络请求模块，网络请求肯定是异步执行的，才会导致dispatch_group_notify未能监听到
（如果处理的是同步的任务，dispatch_group_notify就准确监听全部任务执行完毕）
解决办法
第一种：使用
dispatch_group_enter和dispatch_group_leave
注意点：enter和leave一定要成对出现
#pragma mark - private Method
/// 上传多组图片(支持UIImage或url字符串混合)
/// @param dataArray 内部也是一组数组
/// @param success success
/// @param failure failure
- (void)uploadPhotosWithDataArray:(NSArray <NSArray *>*)dataArray
success:(void(^)(NSArray *result))success
failure:(void(^)(NSString *msg))failure {
/*
dataArray的数据可能是url字符串 或者 UIImage类型
如果是url字符串则不上传
如果是UIImage则上传
*/
// 存储最终结果
__block NSMutableArray *result = [NSMutableArray arrayWithArray:dataArray];
// 创建并发队列
dispatch_queue_t queue = dispatch_queue_create("uploadPhoto_queue",DISPATCH_QUEUE_CONCURRENT);
// 创建队列组
dispatch_group_t group = dispatch_group_create();
for (int i=0; i<dataArray.count; i++) {
// 将每个数组中的UIImage对象转为base64格式
dispatch_group_async(group, queue, ^{
NSArray *row = [result objectAtIndex:i];
NSString *mainDomain = [NSString stringWithFormat:@"https://%@",Domain];
NSMutableArray *tempArr = [NSMutableArray arrayWithArray:row];
NSMutableArray *needUploadArr = [NSMutableArray array];
NSMutableArray *needUploadIndex = [NSMutableArray array];
for (int j=0; j<row.count; j++) {
NSString *url = [row objectAtIndex:j];
// 如果原来的url链接字符串中有域名还需要将域名清空
if ([url isKindOfClass:NSString.class]) {
if ([url hasPrefix:mainDomain]) {
NSString *newUrl = [url stringByReplacingOccurrencesOfString:mainDomain withString:@""];
[tempArr replaceObjectAtIndex:j withObject:newUrl];
}
}
else if ([url isKindOfClass:UIImage.class]) {
NSString *base64String = [LYClassUtils imageToBase64Str:(UIImage *)url maxLength:50];
[needUploadArr addObject:base64String];
[needUploadIndex addObject:@(j)];
}
}
[result replaceObjectAtIndex:i withObject:tempArr];
NSLog(@"%d base - end %@",i,[NSThread currentThread]);
// 请求数据
if (needUploadArr.count > 0) {
// 网络请求模块
# 修改处
dispatch_group_enter(group);
#
[LYNetworkManager uploadImagesWithArray:needUploadArr success:^(id responseObject) {
LYBaseResultModel *responeResult = [LYBaseResultModel mj_objectWithKeyValues:responseObject];
// 上传成功，将原来的UIImage替换成url字符串
if (responeResult.isSuccess) {
NSDictionary *content = [responseObject objectForKey:@"content"];
NSArray *imgs = [content objectForKey:@"headImgArray"];
for (int k=0; k<needUploadIndex.count; k++) {
NSNumber *tempIndex = needUploadIndex[k];
[tempArr replaceObjectAtIndex:tempIndex.integerValue withObject:imgs[k]];
}
[result replaceObjectAtIndex:i withObject:tempArr];
}else{
failure(responeResult.message);
}
// 请求完成执行：发送信号,继续请求
# 修改处
dispatch_group_leave(group);
#
} failure:^(NSError *error) {
// 请求完成执行：发送信号
failure(@"网络异常");
# 修改处
dispatch_group_leave(group);
#
}];
}
});
}
// 监听任务组，如果执行完成，则返回最终结果
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
success(result);
});
}
第二种方法：使用信号量 dispatch_semaphore_t
#pragma mark - private Method
/// 上传多组图片(支持UIImage或url字符串混合)
/// @param dataArray 内部也是一组数组
/// @param success success
/// @param failure failure
- (void)uploadPhotosWithDataArray:(NSArray <NSArray *>*)dataArray
success:(void(^)(NSArray *result))success
failure:(void(^)(NSString *msg))failure {
/*
dataArray的数据可能是url字符串 或者 UIImage类型
如果是url字符串则不上传
如果是UIImage则上传
*/
// 存储最终结果
__block NSMutableArray *result = [NSMutableArray arrayWithArray:dataArray];
// 创建并发队列
dispatch_queue_t queue = dispatch_queue_create("uploadPhoto_queue",DISPATCH_QUEUE_CONCURRENT);
// 创建队列组
dispatch_group_t group = dispatch_group_create();
for (int i=0; i<dataArray.count; i++) {
// 将每个数组中的UIImage对象转为base64格式
dispatch_group_async(group, queue, ^{
# // 创建信号量
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
#
NSArray *row = [result objectAtIndex:i];
NSString *mainDomain = [NSString stringWithFormat:@"https://%@",Domain];
NSMutableArray *tempArr = [NSMutableArray arrayWithArray:row];
NSMutableArray *needUploadArr = [NSMutableArray array];
NSMutableArray *needUploadIndex = [NSMutableArray array];
for (int j=0; j<row.count; j++) {
NSString *url = [row objectAtIndex:j];
// 如果原来的url链接字符串中有域名还需要将域名清空
if ([url isKindOfClass:NSString.class]) {
if ([url hasPrefix:mainDomain]) {
NSString *newUrl = [url stringByReplacingOccurrencesOfString:mainDomain withString:@""];
[tempArr replaceObjectAtIndex:j withObject:newUrl];
}
}
else if ([url isKindOfClass:UIImage.class]) {
NSString *base64String = [LYClassUtils imageToBase64Str:(UIImage *)url maxLength:50];
[needUploadArr addObject:base64String];
[needUploadIndex addObject:@(j)];
}
}
[result replaceObjectAtIndex:i withObject:tempArr];
NSLog(@"%d base - end %@",i,[NSThread currentThread]);
// 请求数据
if (needUploadArr.count > 0) {
// 网络请求模块
// dispatch_group_enter(group);
[LYNetworkManager uploadImagesWithArray:needUploadArr success:^(id responseObject) {
LYBaseResultModel *responeResult = [LYBaseResultModel mj_objectWithKeyValues:responseObject];
// 上传成功，将原来的UIImage替换成url字符串
if (responeResult.isSuccess) {
NSDictionary *content = [responseObject objectForKey:@"content"];
NSArray *imgs = [content objectForKey:@"headImgArray"];
for (int k=0; k<needUploadIndex.count; k++) {
NSNumber *tempIndex = needUploadIndex[k];
[tempArr replaceObjectAtIndex:tempIndex.integerValue withObject:imgs[k]];
}
[result replaceObjectAtIndex:i withObject:tempArr];
}else{
failure(responeResult.message);
}
# 修改处
// 请求完成执行：发送信号,继续请求
dispatch_semaphore_signal(semaphore);
#
} failure:^(NSError *error) {
// 请求完成执行：发送信号
failure(@"网络异常");
# 修改处
dispatch_semaphore_signal(semaphore);
#
}];
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
}
});
}
// 监听任务组，如果执行完成，则返回最终结果
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
success(result);
});
}
参考文章
iOS 使用GCD控制网络请求顺序
GCD dispatch_group_notify线程通知
iOS 使用dispatch_group_enter使多次网络请求依次执行
dispatch_group_enter 使用与讲解
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