NullSafe详细解读

NullSafe个人感觉就是神一般的存在

首先是github地址： https://github.com/nicklockwood/NullSafe
具体干神马用的了 ？？？ ios中网络编程解析json的时候，如果你很不幸遇到了PHP的接口或者遇到了水平不高的Java接口，那是蛋疼无比。。。空字符串是null，空对象是null ，甚至空的数组也是null , 先来段代码压压惊 。。

#import "ViewController.h"@interface NSData (NullTests)- (double)NullTestMethod;@end@implementation NSData (NullTests)- (double)NullTestMethod{    return 47.6;}@end@interface ViewController ()@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    [self testStringValue];    NSLog(@"\n");    [self testFloatValue];    NSLog(@"\n");    [self testIntValue];    NSLog(@"\n");    [self testPointerValue];    NSLog(@"\n");    [self testClass];    NSLog(@"\n");    [self testDescription];    NSLog(@"\n");    [self testRange];    NSLog(@"\n");    [self testCategory]; }- (void)testStringValue{    @try{        id nullValue = [NSNull null];        NSString *result = [nullValue stringValue];        NSLog(@"testStringValue ============ %@ ",result);    }@catch(NSException *e){        NSLog(@"testStringValue eee = %@",e);    }   }- (void)testFloatValue{     @try{         id nullValue = [NSNull null];         __unused float x = floorf(123.456f);         float result = [nullValue floatValue];         NSLog(@"testFloatValue ============ %f ",result);     }@catch(NSException *e){         NSLog(@"testFloatValue eee = %@",e);     }}- (void)testIntValue{     @try{         id nullValue = [NSNull null];         int result = [nullValue intValue];         NSLog(@"testIntValue ============ %d ",result);     }@catch(NSException *e){         NSLog(@"testIntValue eee = %@",e);     }}- (void)testPointerValue{    @try{        id nullValue = [NSNull null];        const void *result = [nullValue bytes];        NSLog(@"testPointerValue ============ %p ",result);    }@catch(NSException *e){        NSLog(@"testPointerValue eee = %@",e);    }}- (void)testClass{    @try{        id nullValue = [NSNull null];        NSString *result = NSStringFromClass([nullValue class]);        NSLog(@"testClass ============ %@ ",result);    }@catch(NSException *e){        NSLog(@"testClass eee = %@",e);    }}- (void)testDescription{    @try{        id nullValue = [NSNull null];        NSString *result = [nullValue description];        NSLog(@"testDescription ============ %@ ",result);    }@catch(NSException *e){        NSLog(@"testClass eee = %@",e);    }}- (void)testRange{    @try{        id nullValue = [NSNull null];        NSRange result = [nullValue range];        NSLog(@"testRange ============ %ld,%ld ",result.length,result.location);    }@catch(NSException *e){        NSLog(@"testClass eee = %@",e);    }}- (void)testCategory{    @try{        id nullValue = [NSNull null];        __unused double x = floor(123.456);        double result = [nullValue NullTestMethod];        NSLog(@"testCategory ============ %lf ",result);    }@catch(NSException *e){        NSLog(@"testClass eee = %@",e);    }}2017-10-11 11:21:41.488769+0800 runtime[27970:7856366] -[NSNull stringValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.488915+0800 runtime[27970:7856366] testStringValue eee = -[NSNull stringValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.488965+0800 runtime[27970:7856366] -[NSNull floatValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489018+0800 runtime[27970:7856366] testFloatValue eee = -[NSNull floatValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489076+0800 runtime[27970:7856366] -[NSNull intValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489155+0800 runtime[27970:7856366] testIntValue eee = -[NSNull intValue]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489193+0800 runtime[27970:7856366] -[NSNull bytes]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489229+0800 runtime[27970:7856366] testPointerValue eee = -[NSNull bytes]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489264+0800 runtime[27970:7856366] testClass ============ NSNull2017-10-11 11:21:41.489344+0800 runtime[27970:7856366] testDescription ============ <null>2017-10-11 11:21:41.489380+0800 runtime[27970:7856366] -[NSNull range]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489441+0800 runtime[27970:7856366] testClass eee = -[NSNull range]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489544+0800 runtime[27970:7856366] -[NSNull NullTestMethod]: unrecognized selector sent to instance 0x1a7a6fef82017-10-11 11:21:41.489599+0800 runtime[27970:7856366] testClass eee = -[NSNull NullTestMethod]: unrecognized selector sent to instance 0x1a7a6fef8

我们发现，操作空对象的时候报各种异常，为了让程序稳定的执行，我将异常try catch处理了，但是按照ios程序猿，try catch用的很少，不像android开发动不动就try一下 ….而且我们发现都是因为对象空引起的异常，如果服务端数据合法合理这些都可以避免，关键是。。。。多少前端程序猿能遇到靠谱的服务端了 ？总之我没遇到几个。。
NullSafe 就要放大招了 。。。。。
你只需要将NullSafe拖入到你的项目中 ，不需要导入
重新运行代码，你会发现。。。。 异常捕获都不走了。。。