之前漏了一篇block形参的介绍,这里给补上。
block形参就是定义block带的参数,和函数的参数使用一样,我们可以在block随意使用修改block形参。
我们来看个例子:
我们声明了两个NSString 指针_p1 _p2、int 型_p3、可变数组_p4,并把这些参数传入block,在block内修改。
-(void )test3 { NSString *_p1=[NSString stringWithFormat:@"hello %@",@"world11"]; NSString *_p2=[NSString stringWithFormat:@"hello %@",@"world12"]; int _p3=1; NSMutableArray *_p4=[[NSMutableArray alloc]init]; //初始值 NSLog(@"init p1:%@,%p,%p",_p1,_p1,&_p1); NSLog(@"init p2:%@,%p,%p",_p2,_p2,&_p2); NSLog(@"init p3:%d,%p",_p3,&_p3); NSLog(@"init p4:%@,%p,%p",_p4,_p4,&_p4); void (^myBlock)(NSString *,NSString **,int,NSMutableArray *) = ^(NSString *p1,NSString **p2,int p3,NSMutableArray * p4) { //block内赋值 p1=@"21"; *p2=@"22"; p3=23; [p4 addObject:@"23"]; NSLog(@"excuteing p1:%@,%p,%p",p1,p1,&p1); NSLog(@"excuteing p2:%@,%p,%p,%p",*p2,*p2,p2,&p2); NSLog(@"excuteing p3:%d,%p",p3,&p3); NSLog(@"excuteing p4:%@,%p,%p",p4,p4,&p4); }; myBlock(_p1,&_p2,_p3,_p4); //block执行后 NSLog(@"excuteafter p1:%@,%p,%p",_p1,_p1,&_p1); NSLog(@"excuteafter p2:%@,%p,%p",_p2,_p2,&_p2); NSLog(@"excuteafter p3:%d,%p",_p3,&_p3); NSLog(@"excuteafter p4:%@,%p,%p",_p4,_p4,&_p4); }
输出日志:
2014-07-31 14:17:06.774 Test[3655:60b] init p1:hello world11,0x16537b20,0x27df8990 2014-07-31 14:17:06.776 Test[3655:60b] init p2:hello world12,0x1652d760,0x27df898c 2014-07-31 14:17:06.778 Test[3655:60b] init p3:1,0x27df8988 2014-07-31 14:17:06.779 Test[3655:60b] init p4:( ),0x1652b6d0,0x27df8984 2014-07-31 14:17:06.781 Test[3655:60b] excuteing p1:21,0x11a08,0x27df893c 2014-07-31 14:17:06.782 Test[3655:60b] excuteing p2:22,0x11a18,0x27df897c,0x27df8938 2014-07-31 14:17:06.783 Test[3655:60b] excuteing p3:23,0x27df8934 2014-07-31 14:17:06.784 Test[3655:60b] excuteing p4:( 23 ),0x1652b6d0,0x27df8930 2014-07-31 14:17:06.785 Test[3655:60b] excuteafter p1:hello world11,0x16537b20,0x27df8990 2014-07-31 14:17:06.786 Test[3655:60b] excuteafter p2:22,0x11a18,0x27df898c 2014-07-31 14:17:06.787 Test[3655:60b] excuteafter p3:1,0x27df8988 2014-07-31 14:17:06.788 Test[3655:60b] excuteafter p4:( 23 ),0x1652b6d0,0x27df8984
从日志可以看出:
我们来看看block对行参变量的处理:
这是block结构体,并没有生成成员 对形参进行引用
struct __KDBlockTest__test3_block_impl_0 { struct __block_impl impl; struct __KDBlockTest__test3_block_desc_0* Desc; __KDBlockTest__test3_block_impl_0(void *fp, struct __KDBlockTest__test3_block_desc_0 *desc, int flags=0) { impl.isa = &_NSConcreteStackBlock; impl.Flags = flags; impl.FuncPtr = fp; Desc = desc; } };
我们看block实现的函数,对变量的访问,都是通过形参来实现的,并没有通过结构体的成员
static void __KDBlockTest__test3_block_func_0(struct __KDBlockTest__test3_block_impl_0 *__cself, NSString *p1, NSString **p2, int p3, NSMutableArray *p4) {
p1=(NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_9; *p2=(NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_10; p3=23; ((void (*)(id, SEL, id))(void *)objc_msgSend)((id)p4, sel_registerName("addObject:"), (id)(NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_11); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_12,p1,p1,&p1); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_13,*p2,*p2,p2,&p2); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_14,p3,&p3); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_15,p4,p4,&p4); }
下面是我们的测试函数,看红色部分,是通过函数参数传递,和函数调用一样,和block内使用局部变量、静态变量、成员变量还是有很大区别的,并没有截获变量。
static void _I_KDBlockTest_test3(KDBlockTest * self, SEL _cmd) { NSString *_p1=((NSString *(*)(id, SEL, NSString *, ...))(void *)objc_msgSend)((id)objc_getClass("NSString"), sel_registerName("stringWithFormat:"), (NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_1, (NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_2); NSString *_p2=((NSString *(*)(id, SEL, NSString *, ...))(void *)objc_msgSend)((id)objc_getClass("NSString"), sel_registerName("stringWithFormat:"), (NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_3, (NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_4); int _p3=1; NSMutableArray *_p4=((id (*)(id, SEL))(void *)objc_msgSend)((id)((id (*)(id, SEL))(void *)objc_msgSend)((id)objc_getClass("NSMutableArray"), sel_registerName("alloc")), sel_registerName("init")); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_5,_p1,_p1,&_p1); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_6,_p2,_p2,&_p2); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_7,_p3,&_p3); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_8,_p4,_p4,&_p4); void (*myBlock)(NSString *,NSString **,int,NSMutableArray *) = (void (*)(NSString *, NSString **, int, NSMutableArray *))&__KDBlockTest__test3_block_impl_0((void *)__KDBlockTest__test3_block_func_0, &__KDBlockTest__test3_block_desc_0_DATA); ((void (*)(__block_impl *, NSString *, NSString **, int, NSMutableArray *))((__block_impl *)myBlock)->FuncPtr)((__block_impl *)myBlock, _p1, &_p2, _p3, _p4);//block 执行 NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_16,_p1,_p1,&_p1); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_17,_p2,_p2,&_p2); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_18,_p3,&_p3); NSLog((NSString *)&__NSConstantStringImpl__var_folders_5l_2l25j3tn0wl_3zy1hpsq1rhc0000gp_T_KDBlockTest_654672_mi_19,_p4,_p4,&_p4); }
总结: