ios - 如何查找图像是否存在 - 解析

Question

我已经成功地从解析中检索到图像(比如说用户个人资料图片)，并且我正在 ios 应用程序中显示它。但是，如果文件栏中没有图像，那么我想显示存储在本地(而不是解析中)的默认图像，不成功。

我的简单问题是，如何检查是否有图像？下面是简单的代码；

PFFile *userImage = [object objectForKey:@"profilePic"]; __block UIImage *userProfilePic =[[UIImage alloc]init];

[userImage getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
    if (!error) {
        //this block will execute only if there is image
        if(data) {
            userProfilePic = [UIImage imageWithData:data];
            userPic.image=userProfilePic;
        }

        //this block is not at all executing. This block should execute when user doesn't have their profile uploaded
        if(!data) {
            UIImage *userProfileDefaultPic = [[UIImage alloc]init];
            userProfileDefaultPic=[UIImage imageNamed:@"defaultprofile.png"];
            userPic.image=userProfileDefaultPic;
        }
    }
}];

希望你能帮助我。提前致谢。

普拉迪普

Answer 1

终于找到解决办法了!

(!data) 不会执行，而是需要检查 PFFile 和存储 PFFile 的 UIImage 是否有图像，如下所示；

PFFile *userImage = [object objectForKey:@"profilePic"];
               __block UIImage *userProfilePic =[[UIImage alloc]init];
if(userImage && ![userProfilePic isEqual:[NSNull null]]) //This is important to check if the file if image is there or not and if not, then display default pic in else part

{
            [userImage getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
                if(!error)
                {

                        userProfilePic = [UIImage imageWithData:data];
                        userPic.image=userProfilePic;

                }
                 }];
            }
            else
            {
                userProfilePic =[UIImage imageNamed:@"defaultprofilepic.png"];
                userPic.image=userProfilePic;

            }