React Native margin acts inside of object, not outside - css

Question

Go to https://snack.expo.io/HJV601djf and open login_screen/components/Form.js. As you can see, the textInput has the style
textInput: {
flex:1,
height: 50,
marginBottom: 20
}
You can see that the user icons are not aligned with the text input. If I take marginBottom out, everything goes ok, but with marginBottom: 20 the icons get dealigned. I can probably fix that by making the text input get aligned vertically too, but I'll not know the cause of the problem.
How can marginBottom affect the insides of UserInput if it's supposed to add space only on the outside?
Printscreen if you don't want to wait to load the app:

Answer 1

This is happening because , in your UserInput.js, you are trying to merge the styles for the textInput while the Image / Icon styles are remaining the same, therefore it is misaligned.
The optimum way to solve this would be to add a textInputContainer style to the component and set the margin to it as
TextInput.js
<View style={mergeObjects(this.props.containerStyle ? StyleSheet.flatten(this.props.containerStyle) : {}, StyleSheet.flatten(styles.inputWrapper))}>
Form.js
<UserInput
containerStyle={styles.textInputContainer}
style={styles.textInput}
source={{uri:'http://www.free-icons-download.net/images/user-icon-74490.png'}}
placeholder="e-mail"
autoCapitalize={'none'}
returnKeyType={'done'}
autoCorrect={false}
/>
and the styles
textInputContainer : {
marginBottom: 20
},
Here's the snack for the same