Objective-C语法之异常处理
Objective-C语法之异常处理
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:- @try {
- <#statements#>
- }
- @catch (NSException *exception) {
- <#handler#>
- }
- @finally {
- <#statements#>
- }
1、新建SomethingException,SomeOverException这两个类,都继承与NSException类。
SomethingException.h- #import <Foundation/Foundation.h>
- @interface SomethingException : NSException
- @end
- #import "SomethingException.h"
- @implementation SomethingException
- @end
- #import <Foundation/Foundation.h>
- @interface SomeOverException : NSException
- @end
- #import "SomeOverException.h"
- @implementation SomeOverException
- @end
2、新建Box类,在某些条件下产生异常。
- #import <Foundation/Foundation.h>
- @interface Box : NSObject
- {
- NSInteger number;
- }
- -(void) setNumber: (NSInteger) num;
- -(void) pushIn;
- -(void) pullOut;
- -(void) printNumber;
- @end
- @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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