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Objective-C 运算符

时间:2014-08-20 21:13 来源:未知 作者:www.51ou.com 阅读:

运算符是一个符号,它告诉编译器执行特定的数学或逻辑操作。 Objective-C语言有丰富的内置运算符并提供了以下几种类型:

  • 算术运算符

  • 关系运算符

  • 逻辑运算符

  • 位运算符

  • 赋值运算符

  • 其他运算符

本教程将逐个讲解算术表达式,关系逻辑,按位分配和其他运算符。

算术运算符

下表列出了所有支持Objective-C语言的算术运算符。假设变量A=10,变量B=20,则:

显示实例

运算符 描述 示例
+ Adds two operands A + B will give 30
- Subtracts second operand from the first A - B will give -10
* Multiplies both operands A * B will give 200
/ Divides numerator by denominator B / A will give 2
% Modulus Operator and remainder of after an integer division B % A will give 0
++ Increment operator increases integer value by one A++ will give 11
-- Decrement operator decreases integer value by one A-- will give 9

关系运算符

下表列出了所有支持Objective-C语言的关系运算符。假设变量A=10和变量B=20,则:

显示实例

运算符 描述 示例
== Checks if the values of two operands are equal or not; if yes, then condition becomes true. (A == B) is not true.
!= Checks if the values of two operands are equal or not; if values are not equal, then condition becomes true. (A != B) is true.
> Checks if the value of left operand is greater than the value of right operand; if yes, then condition becomes true. (A > B) is not true.
< Checks if the value of left operand is less than the value of right operand; if yes, then condition becomes true. (A < B) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand; if yes, then condition becomes true. (A >= B) is not true.
<= Checks if the value of left operand is less than or equal to the value of right operand; if yes, then condition becomes true. (A <= B) is true.

逻辑运算符

下表列出了所有支持Objective-C语言的逻辑运算符。假设变量A=1,变量B=0,那么:

显示实例

运算符 描述 示例
&& Called Logical AND operator. If both the operands are non zero then condition becomes true. (A && B) is false.
|| Called Logical OR Operator. If any of the two operands is non zero then condition becomes true. (A || B) is true.
! Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true, then Logical NOT operator will make false. !(A && B) is true.

位运算符

位运算符位和位操作执行位。 &, |, 和 ^ 真值表如下:

p q p & q p | q p ^ q
0 0 0 0 0
0 1 0 1 1
1 1 1 1 0
1 0 0 1 1

假设,如果A=60和B=13; 现在以二进制格式将如下:

A = 0011 1100

B = 0000 1101

-----------------

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A  = 1100 0011

下表中列出了支持Objective-C语言的位运算符。假设变量A=60和变量B=13,那么:

显示实例

运算符 描述 例子
& Binary AND Operator copies a bit to the result if it exists in both operands. (A & B) will give 12, which is 0000 1100
| Binary OR Operator copies a bit if it exists in either operand. (A | B) will give 61, which is 0011 1101
^ Binary XOR Operator copies the bit if it is set in one operand but not both. (A ^ B) will give 49, which is 0011 0001
~ Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. (~A ) will give -61, which is 1100 0011 in 2's complement form.
<< Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. A << 2 will give 240, which is 1111 0000
>> Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. A >> 2 will give 15, which is 0000 1111

赋值运算符

支持Objective-C语言的赋值运算符有以下:

显示例子

运算符 描述 示例
= Simple assignment operator, Assigns values from right side operands to left side operand C = A + B will assign value of A + B into C
+= Add AND assignment operator, It adds right operand to the left operand and assigns the result to left operand C += A is equivalent to C = C + A
-= Subtract AND assignment operator, It subtracts right operand from the left operand and assigns the result to left operand C -= A is equivalent to C = C - A
*= Multiply AND assignment operator, It multiplies right operand with the left operand and assigns the result to left operand C *= A is equivalent to C = C * A
/= Divide AND assignment operator, It divides left operand with the right operand and assigns the result to left operand C /= A is equivalent to C = C / A
%= Modulus AND assignment operator, It takes modulus using two operands and assigns the result to left operand C %= A is equivalent to C = C % A
<<= Left shift AND assignment operator C <<= 2 is same as C = C << 2
>>= Right shift AND assignment operator C >>= 2 is same as C = C >> 2
&= Bitwise AND assignment operator C &= 2 is same as C = C & 2
^= bitwise exclusive OR and assignment operator C ^= 2 is same as C = C ^ 2
|= bitwise inclusive OR and assignment operator C |= 2 is same as C = C | 2

其他运算符 ↦ sizeof & 三元

一些其他重要的运算符,包括sizeof 和 ? :支持Objective-C语言。

显示示例

运算符 描述 例子
sizeof() Returns the size of an variable. sizeof(a), where a is integer, will return 4.
& Returns the address of an variable. &a; will give actual address of the variable.
* Pointer to a variable. *a; will pointer to a variable.
? : Conditional Expression If Condition is true ? Then value X : Otherwise value Y

Objective-C中的运算符优先级

运算符优先级确定在表达式中的分组。这会影响如何计算一个表达式。某些运算符有比别人更高的优先级,例如,乘法运算符的优先级高于加法运算符:

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