IOS 6 new shortcut initialization notation

Ext.: http://www.2cto.com/kf/201408/328974.html

The following simplified notation is a new formulation after IOS6.0

NSNumber

To simplify the previous wording:

NSNumber *value1;

value1 = [NSNumber numberwithint:12345];

value1 = [NSNumber numberwithfloat:123.45f];

value1 = [NSNumber numberwithdouble:123.45];

value1 = [NSNumber numberwithbool:yes];

The simplified wording:

NSNumber *value2;

value2 = @12345;

value2 = @123.45f;

value2 = @123.45;

value2 = @YES;

Boxing expressions can also be written in similar notation:

NSNumber *pioversixteen1 = [NSNumber numberwithdouble: (M_PI/16)];

NSString *path1 = [NSString stringwithutf8string:getenv ("PATH")];

can be abbreviated as:

NSNumber *pioversixteen2 = @ (M_PI/16);

NSString *path2= @ (getenv ("PATH"));

For string expressions, it is important to note that the value of an expression must not be null, or an exception will be thrown.

Nsarray

For Nsarray initialization, there are a lot of writing, here is no longer one by one listed, we directly see the new wording

Nsarray *array;

Array = @[]; Empty array

Array = @[A]; An array of objects

Array = @[A, b, c]; An array of multiple objects

When the compiler is processing:

Array = @[A, b, c];

Compiler-Generated code:

ID objects[] = {A, b, c};

Nsuinteger count = sizeof (objects)/sizeof (ID);

Array = [Nsarray arraywithobjects:objects count:count];

Note that if the A,b,c object has nil, the runtime throws an exception, which is different from the original processing, so be careful when coding.

Nsdictionary

Similarly, for a dictionary of this data structure, there are many ways to initialize, we look at the new wording:

Nsdictionary *dict;

Dict = @{}; Empty dictionary

Dict = @{@ "Key1": @ "value1"}; A dictionary that contains a key-value pair

Dict = @{@ "Key1": @ "value1", @ "Key2": @ "value" @ "Key3": @ "Value3"}; Dictionary with multiple key-value pairs

Containers built using the above notation are immutable, and if you need to generate a mutable container, you can pass a-mutablecopy message. For example

Nsmutablearray *mutableplanets = [@[

@ "Mercury", @ "Venus", @ "Earth",

@ "Mars", @ "Jupiter", @ "Saturn",

@ "Uranus", @ "Neptune"

] Mutablecopy];

Nsmutabledictionary *dic=[@{@ "Key1": @ "value1", @ "Key2": @ "value" @ "Key3": @ "Value3"} Mutablecopy];

IOS 6 new shortcut initialization notation