IOS-basic development knowledge

IOS-basic development knowledge

The ability of an object to obtain its type at runtime is called introspection. There are multiple methods to achieve this in introspection. Determine the object type-(BOOL) isKindOfClass: classObj determine whether it is an instance of this class or a subclass of this class-(BOOL) isMemberOfClass: classObj determine whether it is instance 1 of this class: person * person = [[Person alloc] init]; // parent class Teacher * teacher = [[Teacher alloc] init]; // subclass // YES if ([teacher isMemberOfClass: [Teacher class]) {NSLog (@ "teacher Teacher class member");} // NO if ([teacher isMemberOfClass: [Person class]) {NSLog (@ "member of the teacher Person class");} // NO if ([teacher isMemberOfC Lass: [NSObject class]) {NSLog (@ "member of the teacher NSObject class");} instance 2: Person * person = [[Person alloc] init]; teacher * teacher = [[Teacher alloc] init]; // YES if ([teacher isKindOfClass: [Teacher class]) {NSLog (@ "teacher is a subclass of Teacher class or Teacher");} // YES if ([teacher isKindOfClass: [Person class]) {NSLog (@ "teacher is a subclass of the Person class or Person");} // YES if ([teacher isKindOfClass: [NSObject class]) {NSLog (@ "te Acher is a subclass of NSObject class or NSObject ");} isMemberOfClass determines whether it belongs to this type of instance and whether it is related to the parent class. Therefore, isMemberOfClass indicates NO when it reaches the parent class; determine the method:-(BOOL) respondsToSelector: selector to determine whether the instance has such a method + (BOOL) instancesRespondToSelector: To determine whether the class has this method. This method is a class method and cannot be used in object instance 3 of the class: // YES teacher is the object if ([teacher respondsToSelector: @ selector (setName:)] = YES) {NSLog (@ "teacher responds to setSize: method");} // YES Teacher is a class if ([Teacher instancesRespondToSelector: @ selector (teach)] = YES) {NSLog (@ "Teacher instance responds to teach method ");}

2: how to determine whether a string is a NULL Character in IOS development

- (BOOL) isBlankString:(NSString *)string {    if (string == nil || string == NULL) {        return YES;    }    if ([string isKindOfClass:[NSNull class]]) {        return YES;    }    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {        return YES;    }    return NO;} 

3. Delete the contents of the Caches folder.

// File Manager NSFileManager * mgr = [NSFileManager defaultManager]; // cache path NSString * caches = [Export (NSCachesDirectory, NSUserDomainMask, YES) lastObject]; [mgr removeItemAtPath: caches error: nil];

4: Calculate the size of a folder or file

/*** @ 15-06-17 09:06:22 ** @ brief calculates the file or folder size. Because the osx Folder does not have a size, you need to calculate the subpathsAtPath from each file to obtain the folder. all files include * @ param filePath In the subfolders, such as the cache caches path * @ return size */-(NSInteger) fileSize :( NSString *) filePath {NSFileManager * mgr = [NSFileManager defaultManager]; // determine whether the file is BOOL dir = NO; BOOL exists = [mgr fileExistsAtPath: filePath isDirectory: & dir]; // The file \ Folder does not exist if (exists = NO) return 0; if (dir) {// self is a folder // traverse all contents in caches --- direct and indirect content NSArray * subpaths = [mgr subpathsAtPath: filePath]; NSInteger totalByteSize = 0; for (NSString * subpath in subpaths) {// obtain the full path NSString * fullSubpath = [filePath stringByAppendingPathComponent: subpath]; // determine whether the file is BOOL dir = NO; [mgr fileExistsAtPath: fullSubpath isDirectory: & dir]; if (dir = NO) {// file totalByteSize + = [[mgr attributesOfItemAtPath: fullSubpath error: nil] [NSFileSize] integerValue];} return totalByteSize;} else {// is a file. return [[mgr attributesOfItemAtPath: filePath error: nil] [NSFileSize] integerValue];} calls to input the following path: NSFileManager * mgr = [NSFileManager ultultmanager]; // cache path NSString * caches = [NSSearchPathForDirectoriesInDomains (NSCachesDirectory, NSUserDomainMask, YES) lastObject];