阅读NSFileManager类API 构思缓存思路

第一部分 文件管理NSFileManager类几个常用的方法

一 比较两个文件的内容是否一样

/* -contentsEqualAtPath:andPath: does not take into account data stored in the resource fork or filesystem extended attributes.

*/

- (BOOL)contentsEqualAtPath:(NSString*)path1 andPath:(NSString*)path2;

二 路径中的文件是否存在

/* The following methods are of limited utility. Attempting to predicate behavior based on the current state of the filesystem or a particular file on the filesystem is encouraging odd behavior in the face of filesystem race conditions. It's far better to attempt an operation (like loading a file or creating a directory) and handle the error gracefully than it is to try to figure out ahead of time whether the operation will succeed.

*/

- (BOOL)fileExistsAtPath:(NSString*)path;

三 移除路径中文件内容

/* These methods replace their non-error returning counterparts below. See the NSFileManagerDelegate protocol below for methods that are dispatched to the NSFileManager instance's delegate.

*/

- (BOOL)removeItemAtPath:(NSString*)path error:(NSError**)error

四 从一个文件中读取数据

/* These methods are provided here for compatibility. The corresponding methods on NSData which return NSErrors should be regarded as the primary method of creating a file from an NSData or retrieving the contents of a file as an NSData.

*/

- (NSData*)contentsAtPath:(NSString*)path;

五 从缓存路径中取出缓存文件内容，该返回值是数组，用数组接收即可

/* subpathsAtPath: returns an NSArray of all contents and subpaths recursively from the provided path. This may be very expensive to compute for deep filesystem hierarchies, and should probably be avoided.

*/

- (NSArray*)subpathsAtPath:(NSString*)path;

六 根据文件名拼接路径

- (NSString*)stringByAppendingPathComponent:(NSString*)str;

七 根据路径计算路径中文件的大小

longlongsize=[fileManagerattributesOfItemAtPath:patherror:nil].fileSize;

第二部分  缓存清理思路的文字描述

第一步 拿到需要清理的缓存文件路径

NSString* filePath =[NSSearchPathForDirectoriesInDomains(NSCachesDirectory,NSUserDomainMask,YES)lastObject];

第二步 创建文件管理者

NSFileManager*fileManager=[NSFileManagerdefaultManager];

第三步 判断缓存文件路径中的文件内容是否存在

if([fileManagerfileExistsAtPath:path])

第四步 遍历缓存路径，拿到路径中所有文件数组

NSArray*childerFiles = [fileManagersubpathsAtPath:path];

第五步  遍历数组，拼接数组

NSString*absolutePath=[pathstringByAppendingPathComponent:fileName];

第六步  计算文件大小

longlongsize=[fileManagerattributesOfItemAtPath:patherror:nil].fileSize;

第七步 删除缓存操作

[[NSFileManagerdefaultManager] removeItemAtPath:patherror:nil];

第三部分 缓存清理思路流程图