- 约1215字
- 技术
- 2017年1月29日
趁过年在家有点时间，从除夕到今天终于把 Code School 里的 Try Objective-C 课程 学习了一遍。虽然之前看过 OC 语法，但一直觉得比较反人类，这次再学习一遍，收获还是不小.前三个级别对我来说比较容易，后面两个级别还是有些难度的。在这里把其中的主要内容做一下笔记，以备下次可以快速复习。
Level 1: NSLog, NSString, NSNumber, NSArray, NSDictionary
NSString *name = @"yanxi";
NSNumber *age = @33;
NSLog(name);
NSLog(@"%@ is %@ years old", firstName, age);
NSArray *apps = @[@"AngryFowl", @"Lettertouch", @"Tweetrobot"];
NSLog(@"%@", apps[1]);
apps[3] = @"Instacanvas"; // 出错了，NSArray is an immutable object.
// 可以重新赋值
apps = @[@"AngryFowl", @"Lettertouch", @"Tweetrobot", @"Instacanvas"];
NSDictionary *appRatings = @{@"AngryFowl": @3, @"Lettertouch": @5};
NSLog(@"%@", appRatings[@"AngryFowl"]);
Lever 2: message, NSUInteger, alloc/init, stringWithFormat
NSArray *foods = @[@"tacos", @"burgers"];
NSLog(@"%@", [foods description]); // Sending a message: [objectName messageName];
NSString *city = @"Ice World";
NSUInteger cityLength = [city length]; // 不含 * 的变量申明
NSLog(@"City has %lu characters", cityLength); // 如果用 %@ 会出错，必须用 %lu
NSNumber *higgiesAge = @6;
NSNumber *phoneLives = @3;
NSNumber *product = higgiesAge * phoneLives; // 出错了
NSUInteger higgiesAgeInt = [higgiesAge unsignedIntegerValue];
NSUInteger phoneLivesInt = [phoneLives unsignedIntegerValue];
NSUInteger higgiesRealAge = higgiesAgeInt * phoneLivesInt;
NSString *newString = @"Hello" + @"World"; // 出错了
NSString *fullName = [firstName stringByAppendingString:lastName];
// 嵌套使用
NSString *fullName = [[firstName stringByAppendingString:@" "] stringByAppendingString:lastName];
// 多参数，后面的参数有名字
NSString *replaced = [fullName stringByReplacingOccurrencesOfString:firstName
withString:lastName];
NSString *copy = [NSString stringWithString:firstName]; // 通过 message 创建 NSString
NSArray *emptyArray = [NSArray array];
NSDictionary *emptyDict = [NSDictionary dictionary];
// alloc/init
NSString *emptyString = [[NSString alloc] init];
NSArray *emptyArray = [[NSArray alloc] init];
NSDictionary *emptyDictionary = [[NSDictionary alloc] init];
NSString *copy = [[NSString alloc] initWithString:otherString];
NSString *fullName = [NSString stringWithFormat:@"%@ %@", firstName, lastName];
Level 3: Bool, if/else, switch/case/break, for, block
Bool mrHiggieIsMean = YES;
// for … in 用法，可用于 NSArray，NSDictionary
NSArray *funnyWords = @[@"Schadenfreude", @"Portmanteau", @"Penultimate"];
for (NSString *word in funnyWords) {
NSLog(@"%@ is a funny word", word);
}
NSDictionary *funnyWords = @{
@"Schadenfreude": @"pleasure derived by someone from another person's misfortune.",
@"Portmanteau": @"consisting of or combining two or more separable aspects or qualities",
@"Penultimate": @"second to the last"
};
for (NSString *word in funnyWords){
NSString *definition = funnyWords[word];
NSLog(@"%@ is defined as %@", word, definition);
}
// code blocks
{
NSLog(@"Hello from inside the block");
}
// 类似于函数（message），可以接受参数，也有返回值
void (^logMessage)(void) = ^{
NSLog(@"Hello from inside the block");
};
void (^sumNumbers)(NSUInteger, NSUInteger) = ^(NSUInteger num1, NSUInteger num2){
NSLog(@"The sum of the numbers is %lu", num1 + num2);
};
void (^myFirstBlock)(NSString *) = ^(NSString *str){
NSLog(str);
};
[newHats enumerateObjectsUsingBlock:
^(NSString *hat, NSUInteger index, BOOL *stop){
NSLog(@"Trying on hat #%lu: %@", index+1, hat);
}
];
Level 4: class, inheritance, property, interface, implementation
Phone.h 创建对象 Phone，继承自 NSObject
@interface Phone : NSObject {
NSNumber *_batteryLife2; // instance variable，外部不可见
}
@property NSString *phoneName; // 属性
@property (readonly) NSNumber *batteryLife; // 只读属性
-(void) speak;
-(NSString *)speak2; // 定义 method/message
-(NSString *)speak3:(NSString *)greeting;
-(void) decreaseBatteryLife:(NSNumber *)arg;
-(void) reportBatteryLife;
@end
Phone.m
#import "Phone.h"
@implementation Phone
- (Phone *)init; // 构造函数，用于初始化
{
_batteryLife = @100;
_batteryLife2 = @100;
return [super init];
}
-(void)speak;
{
NSLog(@"%@ says Hello There!", self);
}
-(NSString *)speak2;
{
NSString *message = [NSString stringWithFormat:@"%@ says Hello There!", self.phoneName];
return self.phoneName;
}
-(NSString *)speak3:(NSString *)greeting;
{
NSString *message = [NSString stringWithFormat:@"%@ says %@", self.phoneName, greeting];
return message;
}
- (void) decreaseBatteryLife:(NSNumber *)arg;
{
_batteryLife = @([self.batteryLife intValue] - [arg intValue]);
_batteryLife2 = @([_batteryLife2 intValue] - [arg intValue]);
}
@end
调用 Phone.h
#import "Phone.h"
Phone *talkingiPhone = [[Phone alloc] init];
talkingiPhone.phoneName = @"Mr. Higgie";
[talkingPhone speck];
NSString *phoneMessage = [talkingiPhone speak2];
NSLog(@"%@", phoneMessage);
NSLog(@"%@", [talkingiPhone speak:@"Hello"]);
level 5: exception, protocol, nil，initXXX, object class, Pointer
判断 copyWithZone: 是否存在
if([talkingiPhone respondsToSelector:@selector(copyWithZone)]){
Phone *copy = [talkingiPhone copy];
[copy reportBatteryLife];
}
Person.h NSCopying protocol 类似于 java 里的接口
@interface Person : NSObject <NSCopying>
@end
Person.m
@implementation Person
- (Person *) copyWithZone:(NSZone *)zone;
{
Person *personCopy = [[Person allocWithZone:zone] init];
return personCopy;
}
@end
nil 表示空，有一个特殊特性，你可以发送 message 给 nil 而不会产生错误，而是返回 nil。
可以自定义初始化函数，名字必须以 init 开头。下面是示例:
Person.h
@interface Person : NSObject
- (Person *) initWithFirstName:(NSString *)firstName
lastName:(NSString *)lastName;
@property NSString *firstName;
@property NSString *lastName;
@end
Person.m
@implementation Person
- (Person *) initWithFirstName:(NSString *)firstName
lastName:(NSString *)lastName;
{
_firstName = firstName;
_lastName = lastName;
return [super init];
}
@end
开闭原则 ：软件中的对象（类，模块，函数等等）应该对于扩展是开放的，但是对于修改是封闭的
object class
// 当 Phone 子类调用 copyWithZone 时，不应该返回 Phone 对象，这时候需要用到 Object class
// 见下面 [self class] 用法
- (Phone *) copyWithZone:(NSZone *)zone;
{
Phone *copy = [[[self class] allocWithZone:zone] initWithBatteryLife:_batteryLife];
copy.phoneName = [NSString stringWithFormat:@"Copy of %@", self.phoneName];
return copy;
}
id 类型
id person = [[Person alloc] init]; // 不需要 *
id person = [[Person alloc] init];
[person setFirstName:@"Eric"]; // id 类型不能用 . 符号
NSLog(@"%@", [person firstName]);
_表示指针，NSString _ 表示指向 NSString object 的指针，或者是一个 NSString object 的引用。 id 类型永远是一个对象的指针，所以不需要加 _ 基本 c 类型变量，比如 int， char 也不需要 _，因为它是直接存值的。如果想 Log 对象的地址，而不是对应的值，将 %@ 修改成 %p 接口。