【Cocoa and Object-c : Up and Running 笔记】04 Object-C 基础语法-阿里云开发者社区

【Cocoa and Object-c : Up and Running 笔记】04 Object-C 基础语法

2014-05-16 924

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简介： 类类标头 @interface Human : NSObject // Define properties and methds @end 类实现 #import "Human.

类

类标头

@interface Human : NSObject
// Define properties and methds
@end

类实现

#import "Human.h"
@interface Human ()
// Define private properties and methods
@end
@implementation Human {
// Define private instance variables
}
// Provide method implementation code
@end

创建一个实例

Human * anObject = [[Human alloc] init];

方法

定义方法

// Returns nothing and has no arguments
- (void)foo;
//Returns an NSString object and takes one argument of type NSObject
- (NSString *)fooWithArgument:(NSObject *)bar;
//Takes two arguments one of type NSObject and a second one of type NSString
- (void)fooWithArgument:(NSObject *)bar andArgument:(NSString *)baz;
// Defines a class method (note the + sign)
+ (void)aClassMethod;

实现方法

- (NSString *)fooWithArgument:(NSObject *)bar{
//Do something here
return retValue;
}

调用方法

[anObject someMethod];
[anObject someMethodWithArg1:arg1 andArg2:arg2];

运算符

算术运算符

比较运算符

逻辑运算符

复合赋值运算符

位运算符

其他运算符

属性

定义属性

@property (attribute1, attribute2) NSString *aProperty;

访问属性

[anObject aProperty];
//Alternative
anObject.aProperty

常量

预处理宏

这并不是一个真正的常量，因为它定义了一个宏在编译之前用真正的值代替所有出现的MAX_NUMBER_OF_ITEMS

#define MAX_NUMBER_OF_ITEMS 10

使用const

一个更好的方法是使用const

NSString *const kMyName = @"Clark";

Static和extern

如果你知道只能在实现文件中使用常量，那么你可以用static。使用static意味着这个常量只能在该文件中可用。

static NSString * const kMyName = @"Clark";

如果你想定义一个全局常量，那么你应该使用extern。

//.h file
extern NSString * const kMyName;

//.m file
NSString * const kMyName = @"Clark";

NSString

示例：

NSString *firstName = @"Clark";
NSString *lastName = @"Kent";
NSString *fullName = [NSString stringWithFormat: @"My full name is %@ %@", firstName, lastName];

NSString格式限定符

NSArray

示例：

//Create an array
NSMutableArray *anArray = [@[@"Clark Kent", @"Lois Lane"] mutableCopy];
//Add new items
[anArray addObject:@"Lex Luthor"];
//Find array length
NSLog(@"Array has %d items", [anArray count]);
//Iterate over array items
for (NSString *person in anArray) {
NSLog(@"Person: %@", person);
}
//Access item with index
NSString *superman = anArray[0];
//Remove Object @"Clark Kent"
[anArray removeObject:@"Clark Kent"];
//Remove the first Object
[anArray removeObjectAtIndex:0];

NSDictionary

示例：

//Create a dictionary
NSMutableDictionary *person = [@{
@"firstname" : @"Clark",
@"lastname" : @"Kent",
@"age" : [NSNumber numberWithInt:35]
} mutableCopy];
//Access values
NSLog(@"Superman's first name is %@", person[@"firstname"]);
//or
NSLog(@"Superman's first name is %@", [person objectForKey:@"firstname"]);
//Find number of items in dicitonary
[person count];
// Add an object to a dictionary
[person setObject:@"job" forKey:@"teacher"];
//Remove an object to a dictionary
[person removeObjectForKey:@"firstname"];

枚举类型

苹果的示例：

每个枚举被赋予一个响应的整数值，所以

typedef enum {
UIButtonTypeCustom = 0,
UIButtonTypeSystem,
UIButtonTypeDetailDisclosure,
UIButtonTypeInfoLight,
UIButtonTypeInfoDark,
UIButtonTypeContactAdd,
UIButtonTypeRoundedRect,
} UIButtonType;

与下述代码一样

typedef enum {
UIButtonTypeCustom = 0,
UIButtonTypeSystem = 1,
UIButtonTypeDetailDisclosure = 2,
UIButtonTypeInfoLight = 3,
UIButtonTypeInfoDark = 4,
UIButtonTypeContactAdd = 5,
UIButtonTypeRoundedRect = 6,
} UIButtonType;

不要求明确地定义第一个枚举的值，并且它默认为0

使用枚举类型

UIButton *button = [UIButton buttonWithType:UIButtonTypeInfoLight];

或者创建一个变量传递到方法，像这样

UIButtonType myButtonType = UIButtonTypeCustom;
UIButton *myButton = [UIButton buttonWithType:myButtonType];

由于它们不是对象，所以你必须打印枚举类型为整数

UIButtonType myButtonType = UIButtonTypeRoundedRect;
// Bad, will give you a warning and might even crash
NSLog(@"%@", myButtonType);
// Good, will properly print the value as an integer
NSLog(@"%d", myButtonType);

流程控制语句

If-else语句

if (someCondition) {
// Execute if the condition is true
} else if (someOtherCondition) {
// Execute if the other condition is true
} else {
// Execute if the none of the above conditions are true
}

三元运算符

someCondition ? @"True" : @"False";

For循环

for (int i = 0; i < totalCount; i++) {
// Do something here
}

While循环

while (someCondition) {
// Do something here
}

Do While循环

do {
// Do something here
} while (someCondition);

Switch语句

switch (aLabel)
{
case kLabelA:
// Execute this if matched
break;
case kLabelB:
// Execute this if matched
break;
default:
// Execute this if matched
break;
}

【Cocoa and Object-c : Up and Running 笔记】04 Object-C 基础语法

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