如何从NSMutableArray循环中添加NSString

Question

I want to add NSString Name in NSmutableArray but I dont know about that. I get 5 NSString name from url in wamp server and I want add these names in NSMutableArray.

this is my code but do not work!!! :

    NSMutableArray *file;
for (int j=0; j < 5; j++) {
        NSString *fileName = [[NSString alloc]initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://192.168.1.101/janatan/filemanager.php?dir=root&file=%d&name",j]]];
        NSLog(@"%@",fileName);
        [file addObject:fileName]  //right???
    } 

Answer 1

You are not allocating NSMutableArray

NSMutableArray *file = [[NSMutableArray alloc] initWithCapacity:5];

If you are not sure about the number of elements gets added to array beforehand, you can use

NSMutableArray *file = [[NSMutableArray alloc] init];

Answer 2

Firstly, the NSMutableArray must be allocated.

Secondly, the using of magic numbers must be avoided.

Next, the readability of code should be improved by replace

NSString *fileName = [[NSString alloc]initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://192.168.1.101/janatan/filemanager.php?dir=root&file=%d&name",j]]];

to something more convenient. Moreover, the memory here is allocated but never released.

Your code may be as follows:

const int numberOfFiles = 5;
NSMutableArray *file = [NSMutableArray array]
for(int i = 0; i < numberOfFiles; ++i){
      NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://192.168.1.101/janatan/filemanager.php?dir=root&file=%d&name", i]];
      NSString *fileName = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
      [file addObject:fileName];
 }

But here are we can find some problems. For example if url is changed on server-side you'd rewrite the code. If the number of elements is changed it's the same. So it would be good to find a way to avoid this kind of dependence.