如何从特定网址下载文件? [英] How to download file from particular url?

问题描述

NSURL * url = @"http://192.168.100.161/UploadWhiteB/wh.txt";
NSData * data = [NSData dataWithContentsOfURL:url];

if (data != nil) {
  NSLog(@"\nis not nil");
  NSString *readdata = [[NSString alloc] initWithContentsOfURL:(NSData *)data ];

我编写此代码是为了从给定的 url 下载文件...但我在线上出现错误
NSData * data = [NSData dataWithContentsOfURL:url];

I write this code to download a file from given url... but i get an error on line
NSData * data = [NSData dataWithContentsOfURL:url];

未捕获的异常...

所以请帮帮我.

推荐答案

你的第一行应该是

NSURL * url = [NSURL URLWithString:@"http://192.168.100.161/UploadWhiteB/wh.txt"];

(NSURL 不是一个字符串，但可以很容易地从一个字符串构造出来.)

(NSURL is not a string, but can easily be constructed from one.)

我希望您在第一行收到编译器警告——忽略编译器警告是不好的.第二行失败，因为 dataWithContentsOfURL: 期望得到一个指向 NSURL 对象的指针，并且当你传递一个你输入的指针时 NSURL*, url 实际上是指向一个 NSString 对象.

I'd expect you to get a compiler warning on your first line--ignoring compiler warnings is bad. The second line fails because dataWithContentsOfURL: expects to be given a pointer to an NSURL object and while you're passing it a pointer that you've typed NSURL*, url is actually pointing to an NSString object.

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