iOS 冷知识

1.placeHolder靠左

建立一个类别，名字自取，并在.h文件中创建一个方法

@interface UISearchBar (MySearchBarPlaceholder)
-(void)changeLeftPlaceholder:(NSString *)placeholder;

.m文件中实现方法

-(void)changeLeftPlaceholder:(NSString *)placeholder {
    self.placeholder = placeholder;
    SEL centerSelector = NSSelectorFromString([NSString stringWithFormat:@"%@%@", @"setCenter", @"Placeholder:"]);
    if ([self respondsToSelector:centerSelector]) {
        BOOL centeredPlaceholder = NO;
        NSMethodSignature *signature = [[UISearchBar class] instanceMethodSignatureForSelector:centerSelector];
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
        [invocation setTarget:self];
        [invocation setSelector:centerSelector];
        [invocation setArgument:&centeredPlaceholder atIndex:2];
        [invocation invoke];
    }
}

在要使用的视图导入类别

    #import "UISearchBar+MySearchBarPlaceholder.m"

在要使用的位置直接调用

    [_searchBar changeLeftPlaceholder:@"企业名称"];