我们知道在mac或iphone上编程最终逃不开os x平台,你无法在windows或linux上开发纯正的apple程序.(so不要舍不得银子买mac啦)虽说linux和windows上有移植的obj-c编译器,但是平台开发框架还是在mac上啊.比如cocoa框架包括Foundation框架,Application Kit框架和Core Data的第三方框架;二cocoa Touch指的则是Foundation,Core Data以及UIKit框架.对于Foundation框架中各个类的使用,可以到apple开发者网站在线查询:https://developer.apple.com/library/mac/navigation/

接下来我们不按顺序,专挑难点,奇怪点和好玩点(如果有的话)的类来看看,直接用代码说话喽

#import<Foundation/Foundation.h>

int main(int argc, char *argv[]){
	@autoreleasepool {
		NSNumber *n;
		NSInteger integer;	//not a class just a typedef

		n = [NSNumber numberWithInteger: 101];
		integer = [n integerValue];
		NSLog(@"%li",(long)integer);

		NSNumber *n1 = [[NSNumber alloc] initWithLong:0x12345678];
		[n1 initWithLong :0xabcd];	//can't change org value 0x12345678!

		integer = [n1 longValue];
		NSLog(@"%lx",(long)integer);

		NSString *str = @"hello apple";
		NSLog(@"str is : %@",str);
		NSLog(@"num is : %@",n);

		NSLog(@"Hello World!");
	}
	return 0;
}

注意代码中%@打印NSNumber型变量的行了吗?有人可能会问这是怎么实现的,我开始也以为%@只能格式化显示NSString类型啊.其实只要类中定义了description方法,就可以以自定义格式显示任何对象的内容啦.这个我们来写个简单类试一下:

#import<Foundation/Foundation.h>

@interface A:NSObject{
	int i;
}
	-(id)init:(int)i_v;
@end

@implementation A
	-(id)init:(int)i_v{
		self = [super init];
		if(self){
			i = i_v;
		}
		return self;
	}

	-(NSString*)description{
		return [NSString stringWithFormat:@"#i is %d#",i];
	}

@end

int main(int argc, char *argv[]){
	@autoreleasepool {
		A *a = [[A alloc] init:99];
		NSLog(@"a is %@",a);
	}
	return 0;
}

注意description方法的实现中stringWithFormat方法的2个参数分割符哦,不是:号而是逗号(,)哦.执行结果如下

wisy@wisy-ThinkPad-X61:~/src/objc_src$ clang -O3 -g0 $OBJ_C_OPT -lobjc -lgnustep-base -o f f.m
wisy@wisy-ThinkPad-X61:~/src/objc_src$ ./f
2014-07-01 12:42:59.380 f[4179] a is #i is 99#

Foundation中的字符串操作看起就显得那么蛋疼,简单的东西给搞的蛮复杂的,尤其是方法名,貌似还驼峰状,我呵呵了.字符串类分为可变和不可变两种,前者类位NSString,后者类为NSMutableString.顾名思义,不可变字符串不可以修改自身,只能返回一个修改后的新字符串,而可变字符串可以修改自身,包括删除subString,拼接啊,替换啊,皆可,下面上代码:

#import<Foundation/Foundation.h>

int main(int argc, char *argv[]){
	@autoreleasepool {
		NSString *str_no_m = @"hello world";
		NSMutableString *str_m;
		NSRange substr;	//just a struct

		str_m = [NSMutableString stringWithString: str_no_m];
		NSLog(@"%@",str_m);

		[str_m insertString: @" xxx" atIndex: 5];
		NSLog(@"%@",str_m);

		[str_m appendString: @" not_fix!"];
		NSLog(@"%@",str_m);

		[str_m deleteCharactersInRange: NSMakeRange(6,4)];	//(index,len)
		NSLog(@"%@",str_m);

		substr = NSMakeRange(6,6);
		[str_m deleteCharactersInRange: substr];
		NSLog(@"%@",str_m);

		substr = [str_m rangeOfString: @"_"];
		if(substr.location != NSNotFound){
			[str_m deleteCharactersInRange: substr];
		}
		NSLog(@"%@",str_m);

		[str_m setString: @"new string!"];
		NSLog(@"%@",str_m);

		substr = [str_m rangeOfString: @"new"];
		if(substr.location != NSNotFound){
			[str_m replaceCharactersInRange: substr withString: @"old"];
		}
		NSLog(@"%@",str_m);

		[str_m setString: @"1122334411223344"];
		[str_m replaceOccurrencesOfString:@"2" withString:@"X" \
			options:0 range:NSMakeRange(0,[str_m length])];
		NSLog(@"%@",str_m);
	}
	return 0;
}

编译及运行结果如下:

wisy@wisy-ThinkPad-X61:~/src/objc_src$ clang -O3 -g0 $OBJ_C_OPT -lobjc -lgnustep-base -o f f.m
wisy@wisy-ThinkPad-X61:~/src/objc_src$ ./f
2014-07-01 14:36:49.380 f[5719] hello world
2014-07-01 14:36:49.382 f[5719] hello xxx world
2014-07-01 14:36:49.382 f[5719] hello xxx world not_fix!
2014-07-01 14:36:49.383 f[5719] hello world not_fix!
2014-07-01 14:36:49.383 f[5719] hello not_fix!
2014-07-01 14:36:49.383 f[5719] hello notfix!
2014-07-01 14:36:49.383 f[5719] new string!
2014-07-01 14:36:49.383 f[5719] old string!
2014-07-01 14:36:49.383 f[5719] 11XX334411XX3344

注意其中的replaceOccurrencesOfString方法,其中的options可能的选项有:

Search and Comparison Options

Several of the search and comparison methods take an “options” argument. This is a bit mask that adds further constraints to the operation. You create the mask by combining the following options (not all options are available for every method):

Search and comparison are currently performed as if the NSLiteralSearch
option were specified.

至于我用的值0,我猜是默认选项吧?因为书上值为nil,编译有警告,遂换为0.