的NSMutableString返回null

问题描述

我想从我的应用程序的文件夹中的文件名构造一个字符串。

I'm trying to construct a string from the file names in my app's document folder.

到目前为止，我有：

NSArray *directoryPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [directoryPaths objectAtIndex:0];
NSError *error = nil;
NSArray *directoryContent = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:documentsDirectory error:&error];

NSLog(@"contents of document folder = %@", directoryContent);

这将打印：

    contents of app's document folder = (
    ".DS_Store",
    File1.doc,
    "File2.pdf",
    ....
)

我想构建的文件名的字符串，由分号以某种方式分离出来，或许，并且通过此code尝试过（最初没有任何分离）：

I'd like to construct a string of file names, separated in some way, perhaps by semi-colon and attempted it (initially without any separation) via this code:

NSMutableString *fileList;
for (NSString *folder in directoryContent)
{
    [fileList appendString:[NSString stringWithFormat:@"%@",  folder]];
}
NSLog(@"file list = %@", fileList);

这版画文件列表=（空），我想不通我要去哪里错了。任何想法？

This prints file list = (null), and I can't figure out where I'm going wrong. Any ideas?

推荐答案

您shold添加字符串前初始化MutableString。 *的NSMutableString =的fileList [的NSMutableString的alloc]初始化];

You shold initialize the MutableString before adding strings. NSMutableString* fileList = [[NSMutableString alloc] init ];

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