iOS Development-oc Language (i) OC data type

share a set of previously learned data from iOS development, followed by a continuous update :

OC Data Type

Data type: base data type, pointer data type

Basic data types: numeric, character (char), Boolean, NULL type (void)

Pointer data type: class, ID

Numeric type: integer type int, float float, double

C and the OC the basic data type

int: Declaring an integer variable

Double: Declaring a two-precision variable

float: Declaring floating-point variables

Char: Declaring a character-type variable

ID: Generic pointer type

Enum: declaring enum type

Long: Declares a variable or function of length integer

Short: Declaring a variable or function with a shorter integer

Signed: Declaring a signed type variable

struct: Declaring struct-body variables

Union: Declaring a common body (union) data type

Unsigned: Declaring an unsigned type variable

void: Declares a function with no return value or no parameter

Data type formatting specifier

Data type OC keyword format description boot character

integer int%d.%i

Short int%hd.%hi

Long, type long int%ld.%li

Unsigned short-integer unsigned int%u

No short integral type unsigned shorter%hu

unsigned long integer unsigned%lu

Float type float%f

Double-%f

Long Double%LF

Character Char-%c

Specific data types

Integer type

The integer type in OC is represented by an int, and the formatted symbol is represented by%i or%d.

For example: int a=100;

The integer constant of the OC language defaults to int, declaring that a long constant can be followed by an "L" or "L", such as:

int B=600;//long c=888888888l;

Type occupies a storage space domain value range

Byte 1 bytes-128-127

Short 2 bytes -2′15-2′15-1

int 4 bytes -2′31-2′31-1

A long 8 byte -2′63-2′63-1

Note: 2 ' 63 is 2 of the 63-time Square

Floating-point types

Variables of floating-point types can store values that include decimals

There are two types of floating-point in OC

float valid numbers for 6-7-bit format notation symbols with%f

double valid numbers are 15-16-bit format notation symbols expressed in%f.%e or%g

The floating-point constant in OC defaults to double, and if you want to declare a constant of float, add F or F after the number

For example: double m=3.14159;//correctly float f=3.14f;

Type occupies a storage space domain value range

Float 4 byte -3.403E38

Double 8 byte -1.798e308-1.798e

string Char

Char data is used to denote "characters" in the usual sense, and the format specifier is expressed in%c

Character constants are single characters enclosed in single quotes,

Example: Char achar= ' a '; char b= ' 0 '; char cchar= ' Apple '; Range: 128-127

"\ n", the OC compiler considers this as a single character

unsigned char domain range: 0~255

The OC characters are Unicode encoded and each character occupies two bytes, so it can be represented in hexadecimal notation.

For example: Char c1= ' \u0061 ';

Note: Unicode is a unified global language encoding

Logic Type Boolean ( boolean )

A Boolean type is a variable used to store true and false values, and is typically used for program flow control.

Boolean data allows for a value of true or FALSE, or an integer of 0 or not 0 instead of true and false, which differs from the Java language.

Instance:

Boolean Flag=true

if (flag)

{

NSLog (@ "Hello iphone");

}

Qualifying words

long int: Declare variable xx as a long integer variable, formatted symbol is ￥%LI, such as: Long int A;

Long Long int: declaration variable xx is a long long integer variable, the format symbol bit%lli, such as: long long int b;

long double: basically the same as int;

unsigned int: declares an unsigned integer variable, such as: unsigned int c;

signed Int: Declares a signed integer variable. such as: Signed int d.

void type (empty type)

Tells the compiler that there are no values of range types

You cannot declare a variable like any other data type

Example: void i=10;//error

Void is usually used in conjunction with methods such as:

-(void) test

{

Code

}

ID type

The ID type is a unique data type in OC that can store any type of object, and in a sense it is a generic object type.

• Declare number as a variable of type ID,

such as: ID number;

• Format specifier:%p

iOS Development-oc Language (i) OC data type