ios UIsearchbar如何使放大镜图片和placeho

直接看效果：
原效果:

居左后：

写一个UIsearchbar 的扩展类，

.h文件

@interface UISearchBar (Extension)
-(void)setLeftPlaceholder:(NSString *)placeholder;
@end

.m文件实现

-(void)setLeftPlaceholder:(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];
}

}