接口裡邊混合：中文 空格 特殊字符...
項目很長時間了，代碼量級很大，想要修改怕是幾天幾夜不能睡覺（稍微誇張）；

那麼有沒有更高效更安全的解決辦法，不用更改一點代碼，答案是：肯定的！！！

解決思路：在執行URLWithString方法的時候，進行處理，那麼就需要運用到runtime上無所不能的，交換方法接口:

eg:

1.www.baidu.com/中文

NSURL *url = [NSURL URLWithString:@"www.baidu.com/中文"];NSLog(@"url=%@",url);

2.www.baidu.com

NSURL *url = [NSURL URLWithString:@"www.baidu.com"];NSLog(@"url=%@",url);

所以這樣兩種情況在項目中會很常見，下面我們用分類的方法來解決這件頭痛的事情：

cmd+N

新建一個分類

cateory.png

url.png

我們知道一個類Class調用的時候最先調用的方法是

加載類的load方法

+ (void)load

開始上代碼：

// NSURL+url.h

//

// Created by 竇心東 on 2017/6/2.

// Copyright © 2017年 竇心東. All rights reserved.

//

#import <Foundation/Foundation.h>

@interface NSURL (url)

+(instancetype)XD_URLWithString:(NSString *)URLString;

@end

// NSURL+url.m

#import "NSURL+url.h"

#import <objc/message.h>

@implementation NSURL (url)

//加載類的load方法

+ (void)load{

NSLog(@"來到這%s",__func__);

//1.拿到兩個方法 蘋果原來的URLWithString 和XD_URLWithString 交換兩個方法

//class_getClassMethod獲取類方法 class_getInstanceMethod獲取對象方法

Method URLWithStr = class_getClassMethod([NSURL class], @selector(URLWithString:));

Method XD_URLWithStr = class_getClassMethod([NSURL class], @selector(XD_URLWithString:));

//2.交換這兩個方法 調用A執行B

method_exchangeImplementations(URLWithStr, XD_URLWithStr);

}

+(instancetype)XD_URLWithString:(NSString *)URLString{

//NSURL *url = [NSURL URLWithString:URLString];

//上邊這一句會出現死循環，因為交換機制調用URLWithString執行XD_URLWithString那麼

//直接調用XD_URLWithString，因為剛才通過了交換，就相當於調用URLWithString，就像大話西遊上移神換影大法

NSURL *url = [NSURL XD_URLWithString:URLString];

if (url == nil) {

NSString * urlstr = [URLString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLFragmentAllowedCharacterSet]];

url = [NSURL URLWithString:urlstr];

// NSLog(@"該URL為空") ;

return url;

}else{

return url;

}

}

@end

#import "ViewController.h"

#import <objc/message.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

//創建一個URL 但是有可能為空

//如果字符串有中文，這個URL就創建不成功，那麼我們發送請求就會出錯 oc中沒有對URL為空的監測機制 Swift裡面有可選項

//我需要為URLWithString這個方法添加一個檢測是否為空的功能 這個在持續好久的項目中作用特別大，不用改動原來的代碼就可以實現

NSURL *url = [NSURL URLWithString:@"www.baidu.com/中文"];

NSLog(@"url=%@",url);

}

- (void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

#運行結果：

2017-06-08 11:27:18.051 06-02 [26223:7685365] 來到這+[NSURL(url) load]

2017-06-08 11:27:18.160 06-02[26223:7685365] url=www.baidu.com/%E4%B8%AD%E6%96%87

over

有個方法值得注意：

[URLStringstringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLFragmentAllowedCharacterSet]];

@interface NSString (NSURLUtilities)

//Returns a new string made from the receiver by replacing all characters not in the allowedCharacters set with percent encoded characters.

UTF-8 encoding is used to determine the correct percent encoded characters.

Entire URL strings cannot be percent-encoded.

This method is intended to percent-encode an URL component or subcomponent string, NOT the entire URL string.

Any characters in allowedCharacters outside of the 7-bit ASCII range are ignored.

返回一個新的字符串由接收方通過替換所有字符與百分比allowedCharacters集編碼字符。utf - 8編碼被用來確定正確的百分比編碼字符。不能percent-encoded整個URL字符串。這種方法旨在percent-encode組件或子組件的URL字符串,而不是整個URL字符串。外的任何字符allowedCharacters 7位ASCII範圍將被忽略。

ios7.0及之後開始添加此方法

- (nullable NSString *)stringByAddingPercentEncodingWithAllowedCharacters:(NSCharacterSet *)allowedCharacters

NS_AVAILABLE(10_9, 7_0);

// Returns a new string made from the receiver by replacing all percent encoded sequences with the matching UTF-8 characters.

返回一個新的字符串由接收方通過替換所有百分比與匹配的utf - 8字符編碼序列。

ios7.0及之後開始添加此屬性

@property (nullable, readonly, copy) NSString *stringByRemovingPercentEncoding NS_AVAILABLE(10_9, 7_0);

- (nullable NSString *)stringByAddingPercentEscapesUsingEncoding:(NSStringEncoding)enc

NS_DEPRECATED(10_0, 10_11, 2_0, 9_0, "Use -stringByAddingPercentEncodingWithAllowedCharacters: instead,

which always uses the recommended UTF-8 encoding,

and which encodes for a specific URL component or subcomponent

since each URL component or subcomponent has different rules for what characters are valid.");

ios9.0及之後開始棄用此方法

使用-stringByAddingPercentEncodingWithAllowedCharacters:相反,它總是使用推薦utf - 8編碼,編碼為一個特定的URL組件或子組件由於每個URL組件或子組件有不同的規則,什麼角色都是有效的。

.

- (nullable NSString *)stringByReplacingPercentEscapesUsingEncoding:(NSStringEncoding)enc

NS_DEPRECATED(10_0, 10_11, 2_0, 9_0, "Use -stringByRemovingPercentEncoding instead,

which always uses the recommended UTF-8 encoding.");

ios9.0及之後開始棄用此方法

使用-stringByRemovingPercentEncoding相反,總是使用推薦的utf - 8編碼。

@end

推薦文章：

http://www.jianshu.com/p/21a21866e379

http://nshipster.cn/nscharacterset/