IOS开发（58）之在 Block Object 中获取变量

1 前言

2 代码实例

#import <Foundation/Foundation.h>
#import "TestDemo.h"
int main(int argc, const char * argv[])
{

@autoreleasepool {
TestDemo *test = [[TestDemo alloc] init];
//        [test log1];
//        [test simpleMethod];
//        [test simpleMethod2];
//        [test simpleMethod3];
//        [test callCorrectBlockObject];
//        [test simpleMethod4];
//        [test log2];
//        [test scopeTest];
[test scopeTest2];
}
return 0;
}

#import <Foundation/Foundation.h>

@interface TestDemo : NSObject

@property (nonatomic, strong) NSString *stringProperty;
-(void)log1;
- (void) simpleMethod;
- (void) simpleMethod2;
- (void) simpleMethod3;
- (void) callCorrectBlockObject;
- (void) simpleMethod4;
-(void)log2;
- (void) scopeTest;
-(void) scopeTest2;
@end

#import "TestDemo.h"

@implementation TestDemo

@synthesize stringProperty;

void (^independentBlockObject)(void) = ^(void){
NSInteger localInteger = 10;
NSLog(@"local integer = %ld", (long)localInteger);
localInteger = 20;
NSLog(@"local integer = %ld", (long)localInteger);
};

-(void)log1{
independentBlockObject();
}
//只读
- (void) simpleMethod{
NSUInteger outsideVariable = 10;
NSMutableArray *array = [[NSMutableArray alloc]
initWithObjects:@"obj1",
@"obj2", nil];
[array sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSUInteger insideVariable = 20;
NSLog(@"Outside variable = %lu", (unsigned long)outsideVariable);
NSLog(@"Inside variable = %lu", (unsigned long)insideVariable);
/* Return value for our block object */
return NSOrderedSame;
}];
}
//可该
- (void) simpleMethod2{
__block NSUInteger outsideVariable = 10;
NSMutableArray *array = [[NSMutableArray alloc]
initWithObjects:@"obj1",
@"obj2", nil];
[array sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSUInteger insideVariable = 20;
outsideVariable = 30;
NSLog(@"Outside variable = %lu", (unsigned long)outsideVariable);
NSLog(@"Inside variable = %lu", (unsigned long)insideVariable);
/* Return value for our block object */
return NSOrderedSame;
}];
}
//获得self
- (void) simpleMethod3{
NSMutableArray *array = [[NSMutableArray alloc]
initWithObjects:@"obj1",
@"obj2", nil];
[array sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSLog(@"self = %@", self);
/* Return value for our block object */ return NSOrderedSame;
}]; }

//无变化Block Object要获得 self需要传参数进去
void (^correctBlockObject)(id) = ^(id self){
NSLog(@"self = %@", self);
};
- (void) callCorrectBlockObject{
correctBlockObject(self); }

//修改类属性
- (void) simpleMethod4{
NSMutableArray *array = [[NSMutableArray alloc]
initWithObjects:@"obj1",
@"obj2", nil];
[array sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSLog(@"self = %@", self);
self.stringProperty = @"Block Objects";
NSLog(@"String property = %@", self.stringProperty);
/* Return value for our block object */
return NSOrderedSame;
}];
}

//在独立 Block Object 内部,你不能使用 dot notation 读写一个已声明属性,在这个场景中可以使用这个合成属性的 getter and setter 方法来代替 dot notation:
void (^correctBlockObject1)(id) = ^(id self){ NSLog(@"self = %@", self);
/* This will work fine */
[self setStringProperty:@"Block Objects"]; /* This will work fine as well */
NSLog(@"self.stringProperty = %@",[self stringProperty]);
};

-(void)log2{
correctBlockObject1(self);
}

//当出现在内联 Block Objects 中,有一条非常重要的规则你必须记住:内联 Block Objects 在其词法区域 会为这些变量复制值。此处发生的事情是在执行 Block 的地方 Block Object 自身一直有一个 integerValue 变量的只读复制。
typedef void (^BlockWithNoParams)(void);
- (void) scopeTest{
NSUInteger integerValue = 10;
/*************** Definition of internal block object ***************/
BlockWithNoParams myBlock = ^{
NSLog(@"Integer value inside the block = %lu", (unsigned long)integerValue);
};
/*************** End definition of internal block object ***************/ integerValue = 20;
/* Call the block here after changing the
value of the integerValue variable */
myBlock();
NSLog(@"Integer value outside the block = %lu",(unsigned long)integerValue);
}

//可改变变量值测试
-(void) scopeTest2{
__block NSUInteger integerValue = 10;
/*************** Definition of internal block object ***************/
BlockWithNoParams myBlock = ^{
NSLog(@"Integer value inside the block = %lu", (unsigned long)integerValue);
};
/*************** End definition of internal block object ***************/ integerValue = 20;
/* Call the block here after changing the
value of the integerValue variable */
myBlock();
NSLog(@"Integer value outside the block = %lu",
(unsigned long)integerValue);
}
@end

3 结语