ios 將NSLog日誌重定向輸出到檔案中儲存

   對於那些做後端開發的工程師來說，看LOG解Bug應該是理所當然的事，但我接觸到的移動應用開發的工程師裡面，很多人並沒有這個意識，查Bug時總是一遍一遍的試圖重現，試圖除錯，特別是對一些不太容易重現的Bug經常焦頭爛額。而且iOS的異常機制比較複雜，Objective-C的語言駕馭也需要一定的功力，做出來的應用有時候挺容易產生崩潰閃退。一遍一遍的用XCode取應用崩潰記錄、解析符號，通常不勝其煩，有時還對著解析出來的呼叫棧發呆，因為程式當時的內部狀態常常難以看明白，只能去猜測。

http://dingran.iteye.com/blog/1773573

http://blog.csdn.net/marujunyy/article/details/12005767

//
//  ZJAppDelegate.m
//  Example
//
//  Created by laizhenjie on 14-5-7.
//  Copyright (c) 2014年 Laizhenjie. All rights reserved.
//

#import "ZJAppDelegate.h"

@implementation ZJAppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [self redirectNSlogToDocumentFolder];
    return YES;
}
							
- (void)applicationWillResignActive:(UIApplication *)application
{
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

#pragma mark - 使用者方法,將nslog的輸出資訊寫入到dr.log檔案中；
// 將NSlog列印資訊儲存到Document目錄下的檔案中
- (void)redirectNSlogToDocumentFolder
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentDirectory = [paths objectAtIndex:0];
    NSString *fileName = [NSString stringWithFormat:@"dr.log"];// 注意不是NSData!
    NSString *logFilePath = [documentDirectory stringByAppendingPathComponent:fileName];
    // 先刪除已經存在的檔案
    NSFileManager *defaultManager = [NSFileManager defaultManager];
    [defaultManager removeItemAtPath:logFilePath error:nil];
    
    // 將log輸入到檔案
    freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stdout);
    freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stderr);
}

@end