Objective-C语法之异常处理
2014-04-07 10:49
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Objective-C的异常比较像Java的异常处理,也有@finally的处理,不管异常是否捕获都都要执行。
异常处理捕获的语法:
[cpp] view
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@try {
<#statements#>
}
@catch (NSException *exception) {
<#handler#>
}
@finally {
<#statements#>
}
@catch{} 块 对异常的捕获应该先细后粗,即是说先捕获特定的异常,再使用一些泛些的异常类型。
我们自定义两个异常类,看看异常异常处理的使用。
[cpp] view
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#import <Foundation/Foundation.h>
@interface SomethingException : NSException
@end
SomethingException.m
[cpp] view
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#import "SomethingException.h"
@implementation SomethingException
@end
SomeOverException.h
[cpp] view
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#import <Foundation/Foundation.h>
@interface SomeOverException : NSException
@end
SomeOverException.m
[cpp] view
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#import "SomeOverException.h"
@implementation SomeOverException
@end
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#import <Foundation/Foundation.h>
@interface Box : NSObject
{
NSInteger number;
}
-(void) setNumber: (NSInteger) num;
-(void) pushIn;
-(void) pullOut;
-(void) printNumber;
@end
[cpp] view
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@implementation Box
-(id) init {
self = [super init];
if ( self ) {
[self setNumber: 0];
}
return self;
}
-(void) setNumber: (NSInteger) num {
number = num;
if ( number > 10 ) {
NSException *e = [SomeOverException
exceptionWithName: @"BoxOverflowException"
reason: @"The level is above 100"
userInfo: nil];
@throw e;
} else if ( number >= 6 ) {
// throw warning
NSException *e = [SomethingException
exceptionWithName: @"BoxWarningException"
reason: @"The level is above or at 60"
userInfo: nil];
@throw e;
} else if ( number < 0 ) {
// throw exception
NSException *e = [NSException
exceptionWithName: @"BoxUnderflowException"
reason: @"The level is below 0"
userInfo: nil];
@throw e;
}
}
-(void) pushIn {
[self setNumber: number + 1];
}
-(void) pullOut {
[self setNumber: number - 1];
}
-(void) printNumber {
NSLog(@"Box number is: %d", number);
}
@end
这个类的作用是,初始化Box时,number数字是0,可以用pushIn 方法往Box里推入数字,每调用一次,number加1.当number数字大于等于6时产生SomethingException异常,告诉你数字达到或超过6了,超过10时产生SomeOverException异常,小于1时产生普通的NSException异常。
这里写 [SomeOverException exceptionWithName:@"BoxOverflowException" reason:@"The level is above 100"异常的名称和理由,在捕获时可以获取。
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- (void)viewDidLoad
{
[super viewDidLoad];
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
Box *box = [[Box alloc]init];
for (int i = 0; i < 5; i++) {
[box pushIn];
[box printNumber];
}
}
打印结果:
Box number is: 1
Box number is: 2
Box number is: 3
Box number is: 4
Box number is: 5
plaincopy
for (int i = 0; i < 11; i++) {
[box pushIn];
[box printNumber];
}
[cpp] view
plaincopy
2012-07-04 09:12:05.889 ObjectiveCTest[648:f803] Box number is: 1
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 2
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 3
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 4
2012-07-04 09:12:05.891 ObjectiveCTest[648:f803] Box number is: 5
2012-07-04 09:12:05.891 ObjectiveCTest[648:f803] *** Terminating app due to uncaught exception 'BoxWarningException', reason: 'The number is above or at 60'
这是时,程序抛出异常崩溃了。那怎么使程序不崩溃呢,做异常处理。
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for (int i = 0; i < 11; i++) {
@try {
[box pushIn];
}
@catch (SomethingException *exception) {
NSLog(@"%@ %@", [exception name], [exception reason]);
}
@catch (SomeOverException *exception) {
NSLog(@"%@", [exception name]);
}
@finally {
[box printNumber];
}
}
运行,程序没有崩溃,打印结果:
[cpp] view
plaincopy
2012-07-04 09:14:35.165 ObjectiveCTest[688:f803] Box number is: 1
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 2
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 3
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 4
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 5
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 6
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 7
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 8
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] Box number is: 9
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] Box number is: 10
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] BoxOverflowException
2012-07-04 09:14:35.225 ObjectiveCTest[688:f803] Box number is: 11
超过10时,SomeOverException异常抛出。
[cpp] view
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@try {
[box setNumber:-10];
}
@catch (NSException *exception) {
NSLog(@"%@",[exception name]);
}
@finally {
[box printNumber];
}
打印结果:
[cpp] view
plaincopy
2012-07-04 09:17:42.405 ObjectiveCTest[753:f803] BoxUnderflowException
2012-07-04 09:17:42.406 ObjectiveCTest[753:f803] Box number is: -10
著作权声明:本文由http://blog.csdn.net/totogo2010/原创,欢迎转载分享。请尊重作者劳动,转载时保留该声明和作者博客链接,谢谢!
更多1
上一篇:Objective-C语法之类和对象下一篇:Objective-C语法之动态类型(isKindOfClass, isMemberOfClass,id)等
异常处理捕获的语法:
[cpp] view
plaincopy
@try {
<#statements#>
}
@catch (NSException *exception) {
<#handler#>
}
@finally {
<#statements#>
}
@catch{} 块 对异常的捕获应该先细后粗,即是说先捕获特定的异常,再使用一些泛些的异常类型。
我们自定义两个异常类,看看异常异常处理的使用。
1、新建SomethingException,SomeOverException这两个类,都继承与NSException类。
SomethingException.h[cpp] view
plaincopy
#import <Foundation/Foundation.h>
@interface SomethingException : NSException
@end
SomethingException.m
[cpp] view
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#import "SomethingException.h"
@implementation SomethingException
@end
SomeOverException.h
[cpp] view
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#import <Foundation/Foundation.h>
@interface SomeOverException : NSException
@end
SomeOverException.m
[cpp] view
plaincopy
#import "SomeOverException.h"
@implementation SomeOverException
@end
2、新建Box类,在某些条件下产生异常。
[cpp] viewplaincopy
#import <Foundation/Foundation.h>
@interface Box : NSObject
{
NSInteger number;
}
-(void) setNumber: (NSInteger) num;
-(void) pushIn;
-(void) pullOut;
-(void) printNumber;
@end
[cpp] view
plaincopy
@implementation Box
-(id) init {
self = [super init];
if ( self ) {
[self setNumber: 0];
}
return self;
}
-(void) setNumber: (NSInteger) num {
number = num;
if ( number > 10 ) {
NSException *e = [SomeOverException
exceptionWithName: @"BoxOverflowException"
reason: @"The level is above 100"
userInfo: nil];
@throw e;
} else if ( number >= 6 ) {
// throw warning
NSException *e = [SomethingException
exceptionWithName: @"BoxWarningException"
reason: @"The level is above or at 60"
userInfo: nil];
@throw e;
} else if ( number < 0 ) {
// throw exception
NSException *e = [NSException
exceptionWithName: @"BoxUnderflowException"
reason: @"The level is below 0"
userInfo: nil];
@throw e;
}
}
-(void) pushIn {
[self setNumber: number + 1];
}
-(void) pullOut {
[self setNumber: number - 1];
}
-(void) printNumber {
NSLog(@"Box number is: %d", number);
}
@end
这个类的作用是,初始化Box时,number数字是0,可以用pushIn 方法往Box里推入数字,每调用一次,number加1.当number数字大于等于6时产生SomethingException异常,告诉你数字达到或超过6了,超过10时产生SomeOverException异常,小于1时产生普通的NSException异常。
这里写 [SomeOverException exceptionWithName:@"BoxOverflowException" reason:@"The level is above 100"异常的名称和理由,在捕获时可以获取。
3、使用Box,在适当添加下捕获Box类的异常
3.1、在没超过6时,没有异常
[cpp] viewplaincopy
- (void)viewDidLoad
{
[super viewDidLoad];
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
Box *box = [[Box alloc]init];
for (int i = 0; i < 5; i++) {
[box pushIn];
[box printNumber];
}
}
打印结果:
Box number is: 1
Box number is: 2
Box number is: 3
Box number is: 4
Box number is: 5
3.2 超过6,产生异常
[cpp] viewplaincopy
for (int i = 0; i < 11; i++) {
[box pushIn];
[box printNumber];
}
[cpp] view
plaincopy
2012-07-04 09:12:05.889 ObjectiveCTest[648:f803] Box number is: 1
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 2
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 3
2012-07-04 09:12:05.890 ObjectiveCTest[648:f803] Box number is: 4
2012-07-04 09:12:05.891 ObjectiveCTest[648:f803] Box number is: 5
2012-07-04 09:12:05.891 ObjectiveCTest[648:f803] *** Terminating app due to uncaught exception 'BoxWarningException', reason: 'The number is above or at 60'
这是时,程序抛出异常崩溃了。那怎么使程序不崩溃呢,做异常处理。
3.3、加上异常处理
[cpp] viewplaincopy
for (int i = 0; i < 11; i++) {
@try {
[box pushIn];
}
@catch (SomethingException *exception) {
NSLog(@"%@ %@", [exception name], [exception reason]);
}
@catch (SomeOverException *exception) {
NSLog(@"%@", [exception name]);
}
@finally {
[box printNumber];
}
}
运行,程序没有崩溃,打印结果:
[cpp] view
plaincopy
2012-07-04 09:14:35.165 ObjectiveCTest[688:f803] Box number is: 1
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 2
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 3
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 4
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] Box number is: 5
2012-07-04 09:14:35.167 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 6
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 7
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] Box number is: 8
2012-07-04 09:14:35.168 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] Box number is: 9
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] BoxWarningException The number is above or at 60
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] Box number is: 10
2012-07-04 09:14:35.169 ObjectiveCTest[688:f803] BoxOverflowException
2012-07-04 09:14:35.225 ObjectiveCTest[688:f803] Box number is: 11
超过10时,SomeOverException异常抛出。
3.4 、小于0时的异常
在Box类的setNumber里,当number小于0时,我们抛出普通异常。[cpp] view
plaincopy
@try {
[box setNumber:-10];
}
@catch (NSException *exception) {
NSLog(@"%@",[exception name]);
}
@finally {
[box printNumber];
}
打印结果:
[cpp] view
plaincopy
2012-07-04 09:17:42.405 ObjectiveCTest[753:f803] BoxUnderflowException
2012-07-04 09:17:42.406 ObjectiveCTest[753:f803] Box number is: -10
著作权声明:本文由http://blog.csdn.net/totogo2010/原创,欢迎转载分享。请尊重作者劳动,转载时保留该声明和作者博客链接,谢谢!
更多1
上一篇:Objective-C语法之类和对象下一篇:Objective-C语法之动态类型(isKindOfClass, isMemberOfClass,id)等
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