iOS字符串处理

拼接字符串

NSString* string;
NSString* string1, string2;
//方法1.
string = [NSString initWithFormat:@"%@,%@", string1, string2 ];
//方法2.(常用)
string = [string1 stringByAppendingString:string2];
//方法3 .
string = [string stringByAppendingFormat:@"%@,%@",string1, string2];

清除字符串 首尾空格及换行符

//清除首尾空格
//定义宏
#define allTrim(object) [object stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]
//调用宏
NSString *emptyString = @"   ";
if ([allTrim( emptyString ) length] == 0 ) {
    NSLog(@"Is empty!");
}

//清除所有空格(替换操作)
NSString *strUrl = [urlString stringByReplacingOccurrencesOfString:@" " withString:@""];

//清除换行字符
headerData = [headerData stringByReplacingOccurrencesOfString:@"\r" withString:@""];
headerData = [headerData stringByReplacingOccurrencesOfString:@"\n" withString:@""];

判断空值处理 (null)与 <null>

//见过最好的解决方法之一, 改进的内联函数，源自Git Hub
// Check if the "thing" pass'd is empty

static inline BOOL isEmpty(id thing) {
    return thing == nil
    || [thing isKindOfClass:[NSNull class]]
    || ([thing respondsToSelector:@selector(length)]
        && [(NSData *)thing length] == 0)
    || ([thing respondsToSelector:@selector(count)]
        && [(NSArray *)thing count] == 0);
}

//判断UITextField.text是否为空
用户未进行任何输入的情况下为nil. (yourTextField.text 在最初创建后的值为nil，nil不等于@"")
[yourTextField.text isEqualToString:@""] || yourTextField.text == nil
//或者
yourTextField.text.length == 0

//其他方法一
//判断字符串是否为空
#define strIsEmpty(str) ([str isKindOfClass:[NSNull class]] || str == nil || [str length] < 1 ? YES : NO )
//方法二
- (BOOL) isBlankString:(NSString *)string {

    if (string == nil || string == NULL) {
        return YES;
    }
    if ([string isKindOfClass:[NSNull class]]) {
        return YES;
    }
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {
        return YES;
    }
    return NO;
}

通过枚举值调对应字符串

//定义枚举类型
typedef NS_ENUM(NSInteger, SubCityCategoryType){
    SomeTypeKey = 0,
};
//声明全局类型数组
extern SomeType const SomeTypes[];
//声明全局类型字符串函数
extern NSString * const SomeTypeIdentifier(SomeType Key);
//定义类型数组
SubCityCategoryType const SubCityCategoryTypes[] = {
    SomeTypeKey
};
//定义字符串函数
NSString * const SubCityCategoryTypeIdentifier(SomeType Key){
    switch (Key) {
        case SomeTypeKey:
            return @"KeyString";
        default:
            return @"";
    }
}
//传入枚举值通过字符串函数获取指定字符串
SubCityCategoryTypeIdentifier(SomeTypeKey) //使用方式

使用JSONKit将字符串，字典，数组转换成json格式

    str = [string JSONString];
    str = [dic JSONString];
    str = [array JSONString];