Wykład 7

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Wykład 7

Mac OS X and iOS operating systems
Lecture 7
Saving data in iOS
Tomasz Idzi
Agenda
NSString and NSData
NSFileManager
Property List
JSON
Core Data
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iOS Directories
App
Documents
Inbox
Library
Caches
temp
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iOS Directories
Directory
Description
Backed up
by iTunes
AppName.app
This directory contains the app and all of its resources.
NO
Documents/
Use this directory to store user-generated content.
YES
Documents/Inbox
Use this directory to access files that your app was asked to open
by outside entities. Such as mail’s attachments.
YES
Library
This is the top-level directory for any files that are not user data
files.
YES
Library/Caches
Subfolder of Library for any caching files.
NO
Tmp/
Use this directory to write temporary files that don’t need to persist
between launches of your app.
NO
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Accessing File Paths
NSArray *paths =
NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docPath = [paths firstObject];
NSString *path = [docPath
stringByAppendingComponent:@”myFile.txt”];
Tomasz Idzi
Writing NSData
BOOL success = [data writeToFile:path
options:NSDataWritingAtomic error:&error];
NSDataWritingAtomic - create temp file first
NSDataWritingWithoutOverwriting - prevent overwriting an existing file
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Reading NSData
[NSData alloc] initWithContentsOfFile: path
options:NSDataReadingMappedIfSafe error:&error];
NSDataReadingMappedIfSafe - file should be mapped into virtual
memory, if possible and safe
NSDataReadingUncached - file should not be stored in the file-system
caches
NSDataReadingMappedAlways - map the file, if possible.
Tomasz Idzi
Writing NSString
BOOL success = [myString writeToFile:path
atomically:YES
encoding:NSUTF8StringEncoding error:&error];
NSUTF8StringEncoding - 8-bit representation of Unicode characters
NSASCIIStringEncoding - Strict 7-bit ASCII encoding within 8-bit chars.
Tomasz Idzi
Reading NSString
[NSData alloc] initWithContentsOfFile:path
encoding:NSUTF8StringEncoding error:&error];
Tomasz Idzi
Writing/Reading NSString and NSData
DEMO
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NSFileManager
NSFileManager *fileManager = [NSFileManager
defaultManager];
Providing a convenient way to:
create
read
move
copy
delete
files and directories.
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NSFileManager
defaultManager];
NSString *documentsPath =
[NSSearchPathForDirectoriesInDomains(NSDocumentDir
ectory, NSUserDomainMask, YES) firstObject];
NSString *filePath = [documentsPath
stringByAppendingPathComponent:@"file.txt"];
BOOL fileExists = [fileManager fileExistsAtPath:filePath];
Tomasz Idzi
NSFileManager - list of files
defaultManager];
NSArray *urls = [fileManager
URLsForDirectory:NSDocumentDirectory
inDomains:NSUserDomainMask];
NSArray *files = [fileManager contentsOfDirectoryAtURL:
[urls firstObject] includingPropertiesForKeys:nil
options:NSDirectoryEnumerationSkipsHiddenFiles
error:&error];
Tomasz Idzi
[fileManager contentsOfDirectoryAtURL:[urls firstObject]
includingPropertiesForKeys:nil
options:NSFileBusy error:&error];
NSFileAppendOnly - The key in a file attribute dictionary whose value
indicates whether the file is read-only.
NSFileBusy - The key in a file attribute dictionary whose value indicates
whether the file is busy.
NSFileCreationDate - The key in a file attribute dictionary whose value
indicates the file's creation date
NSFileType - The key in a file attribute dictionary whose value indicates the
file's type.
NSDirectoryEnumerationSkipsHiddenFiles - Do not enumerate hidden files.
...
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NSPredicate *predicate = [NSPredicate
predicateWithFormat:@"pathExtension == 'png'"];
for (NSURL *fileURL in [contents
filteredArrayUsingPredicate:predicate])
{
// Enumerate each .png file in directory
}
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NSFileManager - create/delete directory
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *documentsPath =
[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) firstObject];
NSString *imagesPath = [documentsPath
stringByAppendingPathComponent:@"images"];
if (![fileManager fileExistsAtPath:imagesPath])
{
[fileManager createDirectoryAtPath:imagesPath
withIntermediateDirectories:NO attributes:nil error:nil];
}
BOOL deleteSucess = [fileManager removeItemAtPath:imagesPath
error:&error];
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NSFileManager - copy/move directory
BOOL success = [fileManager moveItemAtPath:source
toPath:destination error:&error];
BOOL success = [fileManager copyItemAtURL:source
toURL:destination error:&error];
Tomasz Idzi
NSFileManager
DEMO
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Property List
Tomasz Idzi
Property List
XML Property List
Standard Property List
Editable by hand
Device Independent
Binary Property List
Fast loading
ASCII Legacy Property List
Read only
Tomasz Idzi
Property List - supported types
Abstract type
XML element
Cocoa class
Core Foundation type
array
<array>
NSArray
CFArray
dictionary
<dict>
NSDictionary
CFDictionary
string
<string>
NSString
CFString
data
<data>
NSData
CFData
date
<date>
NSDate
CFDate
number - integer
<integer>
NSNumber (intValue)
CFNumber
number - floating point
<real>
NSNumber (floatValue)
CFNumber
Boolean
<true/> or <false/>
NSNumber (boolValue ==
YES or boolValue == NO)
CGBoolean
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Property List - reading
[NSPropertyListSerialization propertyListWithData:data
options:NSPropertyListImmutable
format:&format error:&error];
NSPropertyListImmutable - Specifies that the property list should be
immutable.
NSPropertyListMutableContainers - Causes the returned property list to
have mutable containers but immutable leaves.
NSPropertyListMutableContainersAndLeaves - Causes the returned
property list to have mutable containers and leaves.
Tomasz Idzi
Property List - reading
[NSPropertyListSerialization propertyListWithData:data
options:NSPropertyListImmutable
format:&format error:&error];
NSPropertyListOpenStepFormat - Specifies the ASCII property list
format inherited from the OpenStep APIs.
NSPropertyListXMLFormat_v1_0 - Specifies the XML property list format.
NSPropertyListBinaryFormat_v1_0 - Specifies the binary property list
format.
Tomasz Idzi
Property List - writing
[NSPropertyListSerialization dataWithPropertyList:plist
format:NSPropertyListXMLFormat_v1_0 options:0
error:&error];
Property list must have one object as the root object.
The option parameter is currently unused.
Unsupported types will fail with an error.
Tomasz Idzi
Property List
DEMO
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JSON
JSON stands for JavaScript Object Notation.
It is a human readable format used to transmit data.
JSON is formatted in attribute-value pairs.
It is an alternative to XML for sending data across the network.
Tomasz Idzi
JSON - types
Primitive JavaScript Types: String, Boolean, Number, Null
Arrays are indicated by brackets - []
Objects are indicated by braces - {}
Objects are collection of name-value pairs.
Use commas to add additional fields.
Tomasz Idzi
JSON - NSJSONSerialization
Convert JSON to foundation objects or can convert foundation
to JSON
The top level object is an NSArray or an NSDictionary
All objects are insentence of NSString, NSNumber, NSArray,
NSDictionary or NSNull
All dictionary keys are NSString
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JSON - Decoding
+JSONObjectWithData:options:error:
+JSONObjectWithStream:options:error:
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JSON - Encoding
+dataWithJSONObject:options:error
+writeJSONObject:toStream:options:error
Tomasz Idzi
JSON
DEMO
Tomasz Idzi
Core Data
Managed Object Context
Presistent Store
Managed Objects
Modeling Objects
Fetch Request
Tomasz Idzi

Wykład 7

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