To create an object of a class

Create Object Type

Assign: For non-pointer variables, for underlying data types (such as Nsinteger) and C data types (int, Float,double,char, etc.) plus ID
Such as:
@property (nonatomic,assign) int number

@property (nonatomic,assign) ID Classname;id must be used assign anyway remember: the front does not need to add * to use assign Bar

Strong and weak are the new object variable properties introduced by arc
Xcode 4.2 (IOS sdk4.3 and below) and previous versions use retain and assign, are not arc-supported, Xcode 4.3 (iOS5 and above) have arc, and start using

Starting with IOS5, APPLE?? Native support for JSON
Nsjsonsetialization but to be compatible with previous versions of iOS, you can use a third-party library to parse the JSON

Retain: For pointer variables, you define a variable, and then this variable is changed during the program's run and affects other methods, typically used for strings (nsstring,nsmutablestring) arrays (Nsmutablearray, Nsarray) Dictionary object, view object (UIView) Controller object (Uiviewcontroller), etc.

Set sweep?? The size of the area has an attribute

Setrectofinterestavcapturemetadataoutput a property

Block is to send your request and response to a piece, paired with a pair, so called blocks of code block the advantage is to be able to put the part and the part of the response together, you can easily understand and deal with the disadvantage is if your response part of the improper processing, if you return multiple times, then your code will be messed up, Back when you return the error returned to the other code will quickly appear to run to other processes, the most serious is if the code block never return, then your program is based on the return results to jump page, then you stay in the original page, and will cause memory can not be released

AutoLayout XCODE5 Popularization

Autoresizingmask first used for the ipad inverted screen storyboard and code can be implemented Autolayoutauloayout iOS6 start reference, Xcode4 not to force, not promote the word iOS7 (XCODE5) Start Popularization of sizeclasses interface and AUTOLAYOUT2 core concepts

1 Reference 2 constraints

Create a chat room room xmpproomcoredatastorage *rosterstorage =[[xmpproomcoredatastorage alloc] init];

Xmpproom *room = [[Xmpproom alloc]initwithroomstorage:rosterstorage jid:[xmppjidjidwithstring:@] [email protected] Dispatchqueue:dispatch_get_main_queue ()];

Xmppstream *stream = [self appdelegate].xmppstream; [Activate:stream];
[Configureroomusingoptions:nil];
[joinroomusingnickname:@ "Smith" History:nil];

[Fetchconfigurationform];
[Adddelegate:self Delegatequeue:dispatch_get_main_queue ()];

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Select target, build phases, compile sources, click the Arc file to set the compiler flags to:-FOBJC-ARC

If a project is arc, where to add MRC files:

The same path, and then click MRC File to set compiler flags to:-fno-objc-arc.

To create an object of a class